The basic order: collar, then body, then sleeves

A collar is sewn on before you attach the body pieces to each other. You construct the collar as a separate unit, press it, attach it to the neckline of the front and back pieces, then fold it up and topstitch it down. After that, you sew the shoulder seams, set the sleeves, and finish the side seams. This order matters because the collar sits between two layers of fabric at the neckline, and you need access to both sides while you work.

The collar itself is made from two pieces of fabric cut to the same shape, sewn together on three sides, turned right-side out, and pressed flat. The fourth side—the long edge that attaches to the neckline—stays open until you sew it to the shirt. This open edge is what you'll use to sandwich the neckline seam.

Key Takeaways

  • Cut two identical collar pieces and sew them together on three sides, leaving the neckline edge open, then turn and press before attaching to the shirt.
  • Pin the collar to the right side of the neckline with raw edges aligned, sew it on, then fold the collar up and topstitch the underside down to encase the seam.
  • Grade the seam allowance on the collar (trim one layer shorter than the other) before turning it right-side out so the seam sits flat and doesn't create a bulge.
  • Test your collar fit on a muslin practice garment first if this is your first time, because collar width and shape are hard to adjust after the shirt is sewn.
  • The neckline seam must be smooth and even before you attach the collar, so stay-stitch the neckline first to prevent stretching.

Prepare the neckline before the collar goes on

Stay-stitch the neckline of your front and back pieces before you attach the collar. A stay-stitch is a line of stitching just inside the seam allowance—usually 1/8 inch from the raw edge—that prevents the curved neckline from stretching out of shape while you work. Use a regular stitch length and thread that matches your fabric. This step takes five minutes and prevents the collar from sitting crooked.

Press the neckline seam allowance flat after stay-stitching. You want the neckline to be as smooth as possible before the collar attaches, because any wrinkles or puckers will show through the finished collar.

Construct and press the collar

Place your two collar pieces right sides together and sew along three sides: the two short ends and the outer curved edge. Leave the long neckline edge (the fourth side) unsewn. Use a seam allowance that matches your pattern—usually 5/8 inch—and backstitch at the start and end.

Grade the seam allowance before you turn the collar right-side out. Grading means trimming one layer of the seam allowance shorter than the other—usually trim the under-collar (the piece that will face the inside of the shirt) to 1/4 inch, and leave the upper collar at 5/8 inch. This prevents the seam from creating a ridge along the edge of the finished collar. Trim the corners diagonally close to the stitching line, but do not cut into the threads.

Turn the collar right-side out through the open neckline edge. Use a point turner or the blunt end of a chopstick to push the corners out fully. Press the collar flat, making sure the seam sits exactly on the fold at the edge. Press the open neckline edge flat as well, folding the seam allowance to the inside.

Attach the collar to the neckline

Pin the collar to the right side of the neckline with raw edges aligned. The collar's open edge (with the folded seam allowance inside) should face down toward the body of the shirt. Match the center of the collar to the center front or center back, depending on your pattern, and pin the ends of the collar to the shoulder seams. Pin every inch or so along the curve.

Sew the collar to the neckline using the same seam allowance as your pattern (usually 5/8 inch). Backstitch at the start and end. Use a stitch length of 2.0 to 2.5 mm so the seam is strong enough to hold the collar in place. Sew slowly around the curve and do not stretch the neckline as you feed it under the presser foot.

Press the seam allowance toward the collar (away from the body of the shirt). This helps the collar sit up and away from the neckline.

Fold and topstitch the collar down

Fold the collar up so the right side of the upper collar faces outward and the folded seam allowance of the under-collar wraps around the neckline seam. Pin the folded edge of the under-collar down so it covers the seam line you just sewed. The goal is to encase the raw seam allowance between the two layers of the collar.

Topstitch the under-collar down from the outside of the shirt. Topstitching means sewing a visible line of stitching on the right side of the fabric, usually 1/8 to 1/4 inch from the fold. This line holds the under-collar in place and creates a finished look. Sew slowly and keep the line parallel to the neckline seam. Backstitch at the start and end.

Press the collar one final time after topstitching. The collar should now stand up from the neckline with a clean, finished edge and no raw seams visible from the inside.

Common mistakes that show in the finished collar

If your collar twists or sits unevenly, the neckline was stretched before the collar attached. This is why stay-stitching matters. If you skipped it, you can still fix a twisted collar by carefully unpicking the topstitch, adjusting the under-collar, and re-topstitching, but it is easier to prevent.

If the seam allowance creates a visible ridge along the edge of the collar, you did not grade the seam allowance enough. Grading is not optional—it is what makes the collar lie flat. If this happens on a finished garment, you can trim the under-collar seam allowance closer to the stitching line, but again, it is easier to do it right the first time.

If the topstitch line is wavy or uneven, you were moving too fast or the under-collar was not pinned smoothly. Topstitching is visible, so take your time. If the line is very crooked, unpick it and sew again. A second topstitch line right next to the first is less noticeable than a wavy one.

What comes next: shoulders, sleeves, and sides

Once the collar is complete and pressed, you sew the shoulder seams of the front and back pieces together. The collar sits at the neckline between these two pieces, so the shoulder seams will cross the collar ends. Sew carefully through all layers and backstitch where the collar ends to reinforce.

After the shoulders are sewn, you set the sleeves (if your pattern includes them) and then sew the side seams from armpit to hem. The collar is now locked in place and will not shift.

Frequently Asked Questions

Can I attach the collar after I sew the shoulder seams?

No. The collar must attach to the neckline before the front and back pieces are joined, because you need access to both the right and wrong sides of the neckline. Once the shoulders are sewn, the neckline is a closed circle and you cannot reach inside to fold and topstitch the under-collar down.

What if my collar is too wide or too narrow after I sew it on?

Width is set by your pattern and the collar pieces you cut, so it cannot be adjusted after sewing without unpicking the entire collar. This is why testing on a muslin practice garment is worth the time if you are new to collars. If the collar is too narrow, you can add a second topstitch line closer to the neckline seam to make it appear wider, but this is a workaround, not a fix.

Do I need to interface the collar?

Most patterns call for interfacing in the under-collar to give it structure and help it hold its shape. Check your pattern instructions. If your pattern does not mention interfacing, you can add a lightweight interfacing to the under-collar piece before you sew the two collar pieces together. This is optional for soft, casual shirts but standard for dress shirts.

What stitch length should I use for the collar seams?

Use 2.0 to 2.5 mm (10 to 12 stitches per inch) for all collar seams. This is slightly shorter than a regular seam and makes the collar stronger and less likely to pucker. Do not use a very short stitch (under 1.5 mm) because it can cause puckering on curves.

Why does my topstitch line show on the inside of the shirt?

If the topstitch is visible from the inside, the under-collar did not cover the seam line completely. Unpin the under-collar, adjust it so the fold sits exactly on the seam line, and re-pin before topstitching. The fold should cover the seam, not sit above or below it.