Red Diamond Lattice Mermaid Gown: Free Crochet Pattern

There is something undeniably magical about a mermaid gown. The way it hugs every curve before flaring into a dramatic sweep at the hem, the way it moves when you walk, the way it commands attention without saying a single word. Now imagine that gown crocheted by your own hands, worked in a stunning red diamond lattice stitch that catches the light and draws the eye at every angle. This pattern makes that vision a reality, and the best part is that it is completely free.

Whether you are a seasoned crocheter looking for your next showstopper project or an intermediate maker ready to challenge yourself with something truly extraordinary, this red diamond lattice mermaid gown pattern has everything you need. From yarn recommendations and sizing guidance to detailed stitch instructions and finishing tips, this guide walks you through every step of creating a breathtaking piece that you will wear with pride for years to come.

Why the Diamond Lattice Stitch Is Perfect for a Mermaid Silhouette

The diamond lattice stitch is one of those designs that looks far more complicated than it actually is. At its core, it is built on a combination of chain spaces and double crochet clusters arranged in a repeating diagonal pattern that creates open, airy diamonds across the fabric. This openwork quality is exactly what makes it so well suited to a mermaid gown.

First, the stitch has natural stretch. Because the diamonds are formed through chain loops rather than solid stitches, the fabric gives when you move, making it flattering and comfortable to wear despite the form-fitting silhouette. Second, the visual texture adds dimension without adding bulk. A solid stitch would make a mermaid gown feel heavy, but the lattice keeps the fabric light and elegant. Third, the geometric quality of the diamonds creates a sophisticated, structured appearance that reads as high fashion rather than casual handcraft.

Red is the ideal color choice for this design. In a diamond lattice, color is everything because the open spaces allow the background to show through. A rich, saturated red creates a bold, confident look. If you prefer something more romantic, a deep burgundy or wine shade works beautifully as well. For a more dramatic interpretation, consider a black yarn with red thread woven through the blocking, or a gradient yarn that shifts from coral to deep crimson as the skirt fans out.

Materials You Will Need

Before casting on, gather everything you need so the process flows smoothly from beginning to end.

Yarn: You will need approximately 1,400 to 1,800 yards of fingering weight yarn for a size small/medium gown. For larger sizes, plan for closer to 2,000 to 2,400 yards. Choose a yarn with a silk or mercerized cotton blend if possible, as these fibers drape beautifully and give the stitch definition a polished, fluid look. Pure cotton works well too, though it will be slightly heavier. Avoid bulky or textured yarns for this pattern, as they will obscure the delicate diamond design.

Recommended yarn options include Paintbox Simply DK in Pillar Box Red, Lion Brand Pound of Love in red, Cascade Ultra Pima in ruby, or any smooth, twist-stable yarn in a weight you enjoy working with. If you substitute yarn, always swatch first.

Hook: A US size E (3.5mm) or F (3.75mm) crochet hook works well for most fingering to sport weight yarns in this pattern. The goal is a fabric that drapes without being so loose it loses its structure. Your tension will determine the final hook size.

Notions: A tapestry needle for weaving ends, rust-proof blocking pins, a flexible measuring tape, stitch markers in at least two colors, scissors, and a blocking mat or foam boards. If you plan to line the gown (recommended for comfort and coverage), you will also need coordinating lining fabric, sewing pins, and a needle and thread or access to a sewing machine.

Gauge: 20 stitches and 12 rows equals 4 inches in the diamond lattice pattern after blocking. Always work a gauge swatch of at least 6 by 6 inches, wash and block it the same way you plan to finish the gown, and measure before beginning. An off gauge can mean a gown that fits perfectly or one that is dramatically too large or too small.

Sizing and Measurements

This pattern is written for sizes XS through 3XL. The mermaid silhouette fits close through the bust, waist, and hips before flaring below the knee. Take your measurements carefully before choosing your size.

For the pattern to fit correctly, you need your full bust circumference, your natural waist circumference, your hip circumference at the fullest point, your high hip measurement about three inches below your natural waist, your torso length from the top of your shoulder to your natural waist, your waist to knee measurement, and your desired total length.

The sizing breakdown is as follows. Extra small fits a 32 to 33 inch bust. Small fits 34 to 35 inches. Medium fits 36 to 37 inches. Large fits 38 to 40 inches. Extra large fits 41 to 43 inches. 2XL fits 44 to 46 inches, and 3XL fits 47 to 49 inches.

If your measurements fall between sizes, size up for the bust and plan to adjust the waist with blocking and a lining. The open nature of the diamond lattice stitch makes the gown more forgiving than a solid stitch fabric.

Abbreviations and Stitch Guide

The following abbreviations are used throughout this pattern. Ch means chain. Sl st means slip stitch. Sc means single crochet. Dc means double crochet. Dc2tog means double crochet two together, which is a decrease. Ch-sp means chain space. Rep means repeat. RS means right side. WS means wrong side. Pm means place marker. Sm means slip marker.

The foundation of this pattern is the diamond lattice stitch, which is worked over a multiple of 6 stitches plus 3. Each diamond unit consists of a cluster of two double crochets separated by a chain 2 space, connected to adjacent clusters by chain 2 bridges. The pattern creates diagonal lines that intersect to form the diamond shapes when viewed from a distance.

Special Techniques

Adjustable Ring: Start the top bodice section using an adjustable ring rather than a chain, which allows you to tighten the center completely to avoid a hole.

Join-As-You-Go Rounds: The bodice is worked in joined rounds rather than continuous spirals. At the end of each round, join with a slip stitch to the first stitch, chain up, and continue. This keeps the pattern aligned properly so the diamonds stack correctly.

Short Rows for Bust Shaping: If you are working a size medium or larger, short rows at the back of the bodice create extra room across the shoulder blades without adding length to the front. Instructions for these are included in the pattern notes.

Flare Construction: The skirt flare is achieved through a series of increase rounds spaced at calculated intervals rather than a single dramatic increase row. This gradual shaping gives the classic mermaid silhouette its smooth, controlled flare rather than an abrupt ruffle.

Pattern Instructions

Bodice

Begin at the top edge of the back bodice. Using the adjustable ring method, chain 3. This counts as your first double crochet.

Row 1 (WS): Ch 3, work (dc, ch 2, dc) in the 6th chain from hook, then continue the foundation lattice sequence across to your required stitch count for your size. For size small, your foundation row will contain 85 stitches.

Row 2 (RS): Ch 5, turn. Skip the first dc and the ch-2 sp, work dc in the next dc. Ch 2, skip the next dc, work (dc, ch 2, dc) in the ch-2 sp of the next diamond unit, ch 2, skip the next dc, dc in the next dc. Rep from across, ending ch 2, dc in the top of the turning chain.

Row 3: Ch 5, turn. Dc in the first ch-2 sp. Ch 2, dc in the next dc, ch 2, dc in the next ch-2 sp. Rep from across, ending with dc in the 3rd chain of the turning chain.

Rep rows 2 and 3, alternating, for the required bodice length. For a gown with a straight neckline, work until the bodice measures 10 inches from the foundation row. For a sweetheart neckline, follow the shaping instructions in the next section.

Sweetheart Neckline Shaping (Optional)

At the center front of the bodice, work decreases over 6 rows to create the V shape. Place markers at each side of the center front 12 stitches. Work to the first marker, dc2tog, continue to second marker, dc2tog, work to end. Repeat this decrease every RS row three times total, then shape the curved outer edges with slip stitches at the beginning of every other row until the sweetheart cup is formed. This technique requires careful counting but creates a beautiful result.

Waist Shaping

Once the bodice is complete, do not fasten off. You will work the waist shaping in joined rounds from this point forward, so the gown transitions from flat construction to in-the-round here.

Join the side seams of the bodice with a row of slip stitches worked through both layers, or use the mattress stitch method with your tapestry needle for an invisible seam. Then join yarn to the bottom edge of the bodice and begin working in rounds.

Round 1: Work a single crochet in each stitch and chain space around the bottom edge of the bodice. Join with sl st to first sc. Chain 3.

Rounds 2 through 6: Work in the diamond lattice pattern in rounds, maintaining pattern alignment. These rounds sit at the natural waist and are worked without increase or decrease to let the gown follow the body’s natural curve.

For waist suppression on sizes medium and above, work one dc2tog on each side of the body at the waist position at the beginning of round 3. This subtle shaping pulls the fabric gently inward and creates definition.

Hip Shaping

The hip section of the gown is worked below the waist over approximately 10 to 14 rounds depending on your torso length. No increases are added here, because the lattice stitch naturally relaxes slightly as it descends from the waist, accommodating the hip measurement.

If your hip measurement is more than 10 inches larger than your waist, you may need to add a discreet increase round at the fullest hip point. To do this, add one chain 1 space within each diamond unit on one increase round, effectively adding 6 stitches per repeat around the gown.

Mermaid Flare

The mermaid flare begins approximately at the knee, which for most wearers falls about 22 to 26 inches below the natural waist. The exact point where you begin the flare depends on your height and preferred silhouette. A flare that begins higher up creates a more dramatic, ball-gown-adjacent look. A flare that starts lower gives a sleeker, more minimalist mermaid shape.

Flare Round 1: Work the diamond lattice pattern as established, but increase each chain-2 space to a chain-3 space. This opens the fabric slightly.

Flare Round 2: Work two diamond units in the space where one existed in the previous round at 6 evenly spaced points around the gown. Place stitch markers at these points in round 1 to keep them aligned.

Flare Rounds 3 through 8: Continue increasing at the marked points every other round, adding one diamond unit per section each time.

Flare Rounds 9 through finish: Work even in the expanded pattern until the gown reaches your desired length. The final two rounds are worked in solid double crochet to create a firm, polished hem edge. Work one round of reverse single crochet for a corded finish that lies flat and resists curling.

Finishing and Blocking

Blocking is not optional with this pattern. It is essential. The diamond lattice stitch will look slightly uneven and compressed before blocking and absolutely stunning after it. Do not skip this step.

Soak the finished gown in cool water with a small amount of wool wash or gentle soap for at least 20 minutes. Gently press out the excess water by rolling the gown in a clean towel. Never wring or twist the fabric.

Lay the gown flat on your blocking mat. Starting from the bodice, pin the top edge to your measurements. Work your way down, smoothing and pinning the lattice diamonds into even, symmetrical shapes. The diamonds should be roughly square at the bodice and may elongate slightly in the flared sections to enhance the flowing silhouette.

Allow the gown to dry completely, which may take 24 to 48 hours depending on your climate. Once dry, remove the pins and hang the gown on a padded hanger to settle.

Lining Your Gown

A crochet gown, especially one worked in an open lattice stitch, benefits enormously from a lining. The lining provides coverage, prevents the gown from clinging uncomfortably to skin or undergarments, and gives the outer crochet fabric something to lay against that enhances its drape and structure.

Choose a lightweight lining fabric in a color that coordinates with your yarn. A deep red or wine satin creates a romantic, layered effect. Nude or blush lining is the most practical for versatility. Black lining creates drama and makes the red lattice pop with incredible contrast.

Cut the lining to match the gown’s silhouette, adding seam allowances at all edges. Sew the lining along the side seams, then slip it inside the gown with wrong sides facing. Hand stitch the lining to the inside of the bodice at the neckline and armhole edges, and hem the lining about one inch shorter than the gown’s outer edge so it does not peek out at the hem.

Styling and Wearing Your Red Diamond Lattice Mermaid Gown

This gown is a statement piece that deserves equally intentional styling. For an evening event or formal occasion, pair it with strappy heeled sandals, a sleek updo, and minimal jewelry. The gown’s texture is so rich that it does its own heavy lifting aesthetically, and simple accessories let it breathe.

For a more editorial or fashion-forward look, layer the gown over a fitted turtleneck bodysuit in black or red, and add chunky boots that peek out from the hem. This unexpected pairing makes the crochet fabric feel contemporary and fashion-forward rather than purely romantic.

For photographs, the gown looks breathtaking outdoors in natural light, particularly against neutral backgrounds like stone walls, sandy beaches, or muted greenery. The red reads with incredible vibrancy in both natural and golden-hour lighting.

Tips for Staying Motivated on a Big Project

A full-length gown is one of the most ambitious things a crocheter can make, and it is natural to feel overwhelmed at some point in the process. A few strategies that help are breaking the project into clear phases such as completing the bodice, then the waist, then the hip section, and finally the flare, and celebrating each phase as its own accomplishment.

Set aside regular project time rather than waiting for large blocks of free time, because consistency matters far more than marathon sessions. Keep a project journal where you track your round counts, note any modifications you make, and record your yarn usage. This makes it much easier to troubleshoot if something seems off, and it becomes a lovely record of the making process once the gown is complete.

Finally, try the gown on as you go. Because the construction is in-the-round from the waist down, you can slip it on at any point to check fit, length, and proportion. Catching a fitting issue early is infinitely easier than discovering it after you have completed another eight inches of flare.

Sharing Your Make

When you finish your red diamond lattice mermaid gown, share it with the crochet community. Tag your project on Ravelry or Instagram so other makers can find inspiration and see the many beautiful variations this pattern inspires. Consider photographing your work in progress as well, because the pattern’s texture evolves so beautifully at every stage that the journey is as worth documenting as the finished piece.

This pattern is free to use for personal projects and small handmade sales. If you sell finished garments made from this pattern, please credit the design. Do not reproduce or distribute the pattern itself as your own work.

Now gather your yarn, wind your cake, sharpen your hook, and begin. The mermaid gown of your dreams is waiting to be made, stitch by stitch, diamond by diamond, in the most beautiful shade of red you can find.