Emerald Diamond Lattice Mermaid Gown: Free Crochet Pattern
There is something undeniably magical about a mermaid gown. The way it hugs the body through the torso, flares dramatically at the hem, and moves with every step like it has a life of its own — it is the kind of garment that makes people stop and stare. Now imagine that same silhouette rendered entirely in crochet, worked in a deep, jewel-toned emerald green, with a diamond lattice stitch that catches the light and creates an intricate geometric pattern across the entire body. That is exactly what this free crochet pattern gives you: the Emerald Diamond Lattice Mermaid Gown.
This pattern is designed for intermediate to advanced crocheters who are ready to take on a full-length statement piece. Whether you are making it for a styled photo shoot, a special occasion, a fashion editorial, a beach cover-up, or simply because you want to prove to yourself that you can — this gown is worth every single stitch. Read through the entire pattern before you begin, gather your materials, swatch carefully, and then settle in for one of the most rewarding projects you will ever take on.
About This Pattern
The Emerald Diamond Lattice Mermaid Gown is a floor-length crocheted dress worked from the top down. The bodice is close-fitting and structured, the waist is subtly cinched, and the skirt begins to flare below the knee, creating that iconic mermaid silhouette. The diamond lattice stitch used throughout the body is both breathable and visually stunning, making it appropriate for warmer seasons or layering over a slip dress in cooler weather.
The entire gown is worked as a single continuous piece wherever possible to minimize seaming. The straps and back are adjustable, and the flared hem incorporates strategic increases to achieve maximum drama without distorting the stitch pattern. This pattern is written for a size small with notes for modifying to other sizes throughout.
Materials You Will Need
For this pattern, you will need approximately 1,800 to 2,400 yards of a DK weight yarn in emerald green. The exact yardage will depend on your gauge and your finished size. The original gown was made using a cotton-bamboo blend yarn, which gives the lattice stitch beautiful drape and a subtle sheen that really enhances the jewel-tone color. Pure cotton works wonderfully as well, though it will be slightly heavier. Avoid very stretchy yarns for this project, as the diamond lattice requires a stable stitch structure to hold its shape.
You will need a 3.75 mm crochet hook, though you may need to size up or down to achieve gauge. A set of stitch markers will be essential for tracking your decrease and increase points throughout the bodice shaping. You will also want a tapestry needle for weaving in ends, a measuring tape, and a piece of lining fabric or a slip dress to wear underneath, since the lattice creates an open fabric. Scissors, pins for blocking, and blocking mats or towels will round out your toolkit.
Optional but highly recommended: a row counter, a dress form or mannequin for fitting as you go, and a friend who can help you measure the back of the bodice.
Gauge
Before you begin the gown itself, please swatch. Gauge matters enormously for a fitted garment, and getting it right from the start will save you hours of frustration later.
Your target gauge is 18 stitches and 20 rows to 4 inches (10 cm) in the diamond lattice stitch pattern, after blocking. If your gauge is tighter, go up a hook size. If your gauge is looser, go down a hook size. Wash and block your swatch before measuring, since cotton and bamboo blends can relax considerably after their first wash.
Abbreviations Used in This Pattern
Throughout the pattern, the following abbreviations apply: ch means chain, sl st means slip stitch, sc means single crochet, dc means double crochet, hdc means half double crochet, ch-sp means chain space, sk means skip, rep means repeat, pm means place marker, and RS means right side. The diamond lattice stitch is abbreviated as DLS throughout the written instructions.
Understanding the Diamond Lattice Stitch
The diamond lattice stitch is the heart of this entire gown, and it is worth spending some time getting comfortable with it before you dive into the full project. Work a practice swatch of at least 30 stitches wide and 30 rows tall. You will start to see the diamonds emerge after just a few repeats, and by the time your swatch is done, your hands will know the rhythm by heart.
The stitch works on a multiple of 4 plus 2 foundation chain. Each diamond unit spans 4 stitches and 4 rows, creating a balanced geometric shape. The stitch alternates between crossed double crochets and chain spaces in a way that builds the diamond shape without any complicated post stitches or specialty techniques. Once the rhythm clicks, it flows beautifully and works up faster than it looks.
To work the diamond lattice swatch: chain 34. Row 1 (RS): sc in second ch from hook and in each ch across. Turn. (33 sc) Row 2: ch 3, dc in first st, sk 1 st, sc in next st, sk 1 st, and continue across, ending with 2 dc in last st. Turn. Continue the pattern, building the lattice as described in each section below. Full written row-by-row instructions are included within each section of the gown.
Pattern Instructions: The Bodice
The bodice of the gown is worked flat in two panels, a front and a back, which are then joined at the side seams. This approach makes fitting much easier and allows you to adjust width independently for the front and back if needed.
Front Bodice Panel
Begin with a foundation chain of 46 chains for size small. This creates the width across the front bust. If you are modifying for a larger size, add 4 chains per size increment (50 for medium, 54 for large, 58 for extra large). The bodice is designed with approximately 2 inches of negative ease for a snug, structured fit.
Row 1 (RS): sc in second ch from hook and in each ch across. Turn. (45 sc)
Row 2: ch 3, turn, dc in first st, ch 1, skip 1 st, dc in next st. Continue across in pattern, working ch 1 spaces and dc posts to begin establishing the lattice grid. End with 2 dc in last st. Turn.
Rows 3 through 6 establish the first full diamond repeat. Work as follows: each right-side row builds the upper half of the diamond by placing crossed dc units at the center of each chain space from the previous right-side row, while each wrong-side row fills the lower half with sc anchors. The alternating structure of sc and dc rows is what creates the geometric diamond illusion.
Continue in the established diamond lattice pattern for 10 inches total from foundation, or until piece measures the distance from the top of the bodice to approximately 1 inch below the natural waist. End after completing a wrong-side row.
Waist Shaping
The waist shaping is worked by decreasing 2 stitches at each side edge over the next 6 rows, creating gentle inward shaping. Use sc2tog at the beginning and end of each RS row during this section. You will lose a total of 12 stitches across the waist section. After the waist decreases are complete, continue even in pattern for 2 more inches, then work 6 rows of increases (2 stitches per edge per RS row) to re-establish the hip width. At the end of the hip section, your stitch count should be back to your starting number.
Back Bodice Panel
Work the back bodice panel exactly as the front, but when you reach 5 inches from the foundation (the approximate mid-bust height), divide for the back opening. The back of the gown features a center opening that runs from the top of the bodice to the waist, which is finished with a simple single crochet edging and closed with a series of small button loops or a length of satin ribbon woven through the lattice for a lace-up effect.
To divide for the back opening, work across to the center stitch, turn, and work each half of the back bodice separately from this point until the back measures the same as the front at the hip. You will work right half, fasten off, rejoin yarn at center, and work left half separately.
Joining the Side Seams
Once both panels are complete through the hip section, align the front and back panels with right sides facing and use a slip stitch seam along both side edges from the underarm to the hip. Leave the underarm edges open for now. Weave in your ends and turn the bodice right side out. At this point you should have a tube-shaped bodice that, when tried on, fits snugly through the bust and has gentle waist shaping with hip room.
Straps
The straps are worked separately and attached at the front and back bodice upper edges. Work two straps, each approximately 12 inches long, in a narrow 5-stitch wide single crochet column. The length can be adjusted depending on your torso height and shoulder width. Attach each strap at the front upper corners and cross the straps in back, attaching at the opposite back upper corners for a criss-cross back effect. Alternatively, work straight straps for a more classic silhouette. A row of sc edging around the entire upper bodice, including the back opening edges, finishes everything neatly.
Pattern Instructions: The Skirt
The skirt is where this gown truly comes alive. It is worked in the round, attached to the lower edge of the bodice, and worked downward to the floor. The magic of the mermaid silhouette comes from working even through the thigh area and then introducing dramatic increases at the knee level that send the fabric flaring outward.
Attaching the Skirt
With right side facing, attach yarn to the lower edge of the joined bodice at one side seam. Work a joining round of sc evenly around the entire lower edge of the bodice, placing one sc in each stitch and one sc in each row end along the side seam edges. Join with sl st to first sc. This becomes the foundation round for the skirt. Count your stitches and make a note of the total, as this is your starting stitch count for the skirt.
Hip and Thigh Section
Work the hip and thigh section of the skirt even in the round, maintaining the diamond lattice pattern throughout. Because you are now working in the round rather than flat, you will need to adjust slightly: each round is a right-side round, so the pattern is worked continuously. Join at the end of each round with a sl st and turn, or work in a continuous spiral by dropping the joining and simply working around. The turning method produces a cleaner lattice alignment and is recommended.
Continue even in the hip and thigh section for approximately 14 to 18 inches, depending on your height and where you want the flare to begin. For someone around 5 foot 6, the flare typically looks best starting about 14 inches below the hip. For a taller person, add a few more inches before beginning the increases. Use a measuring tape to check against your own body or a dress form.
The Mermaid Flare
This is the most exciting section of the entire gown, and it is all built on a simple principle: strategic, regular increases that spread the stitch count outward while maintaining the integrity of the diamond pattern.
Begin the flare section by working an increase round: work in pattern across to each point where the diamond lattice creates a natural apex (the top point of each diamond shape), and work 2 sc in that single apex stitch instead of 1. This naturally integrates the increase into the geometry of the pattern and helps new diamonds begin without awkward distortion.
Work one even round between each increase round, and continue alternating increase rounds and even rounds for 8 rounds total. By this point your stitch count will have grown substantially and the skirt will be visibly spreading outward.
After the first 8 rounds of gradual increase, shift to working an increase every round for the next 6 rounds. The fabric will now be flaring dramatically, and the hem circumference will be expanding rapidly. This is the section that creates the iconic dramatic sweep of a mermaid gown.
The Hem Ruffle
In the final 6 inches before the hem, transition from the diamond lattice to a slightly denser stitch to give the hem structure and weight. Work 3 rounds of dc in each stitch, increasing on every round. This creates a dense, full ruffle at the hem that holds its shape beautifully and swishes magnificently when you walk.
Finish the very last round with a simple sc border for a clean edge, or work a shell stitch edging for a more decorative finish. A shell stitch edge (work 5 dc in every other stitch, skip one stitch, sc in next, repeat) complements the geometric lattice beautifully and adds one final flourish to an already extraordinary garment.
Finishing the Gown
Weave in all remaining ends thoroughly, especially any ends along the skirt joining round, as these are under stress when the gown is worn and need to be secure. Block the entire gown by soaking it in cool water with a drop of gentle wool wash (even for cotton, this helps relax the fibers), pressing out excess water carefully without wringing, and laying it flat to dry on blocking mats with the skirt spread to its full width.
Blocking will transform the gown completely. The diamond lattice opens up, the drape becomes fluid, the emerald color blooms, and the entire piece takes on a professional, polished quality that is simply stunning. If you have a dress form, put the gown on it while slightly damp so it dries in shape.
For the back closure, weave a length of satin ribbon in emerald green or deep gold through the lattice along the back opening edges for a lace-up effect, or sew a series of tiny button loops along one edge and attach small buttons along the other. Either approach is beautiful and allows the gown to be adjustable.
Sizing and Modification Notes
This pattern as written fits a 34-inch bust, 27-inch waist, and 37-inch hip (size small). To modify for other sizes, add 4 chains per size to the bodice foundation and adjust the waist decrease and increase counts proportionally. The skirt circumference is naturally flexible since it is attached to the bodice edge and can be adjusted at the joining round by adding or subtracting stitches in the joining sc round.
For length modifications, simply work more or fewer rounds in the hip and thigh section before beginning the flare. The flare section itself can remain the same regardless of length modification.
Care Instructions
Hand wash in cool water with a gentle detergent designed for delicate fabrics. Do not wring or twist. Press out water by rolling in a clean towel. Lay flat to dry away from direct sunlight, which can fade even the most vibrant emerald yarns over time. Steam blocking periodically will refresh the drape and stitch definition beautifully.
A Few Final Thoughts
The Emerald Diamond Lattice Mermaid Gown is not a weekend project, and it is not meant to be. It is a labor of love that rewards patience, careful attention to gauge, and a willingness to try things on frequently as you work. Every inch of this gown is an accomplishment, and by the time you reach the final hem ruffle, you will have created something genuinely extraordinary.
Wear it over a satin slip for an evening event. Layer it over a swimsuit for a beach shoot. Display it as wearable art. Style it with sandals or heels or bare feet on a summer evening. However you choose to wear this gown, know that you made it by hand, one stitch at a time, in the most beautiful shade of green the crochet world has ever seen.
Share your finished gown on social media and tag your work so others can see what you have created. Leave a comment below if you have questions about the pattern, and happy crocheting.
