The basic sleeve seam runs from your underarm to your wrist
Sewing a sleeve means joining the fabric tube of the sleeve to the armhole of your garment body. The seam runs down the inside of your arm from underarm to wrist (or wherever the sleeve ends). You'll pin the sleeve to the armhole with the right sides of the fabric facing each other, then sew along that curved edge. The sleeve cap — the curved part at the top — is the trickiest bit because it has to curve smoothly around your shoulder without puckering.
Most sleeves are sewn before the side seams of the garment are closed. This gives you room to work and lets you adjust the fit. Once both sleeves are attached, you'll sew the underarm seam in one long line from cuff to side seam.
Key Takeaways
- Pin the sleeve cap to the armhole with right sides together, starting at the shoulder seam and working toward the underarm, easing in fullness as you go.
- Use a 5/8-inch seam allowance (the standard for garment sewing) and sew slowly around the curved armhole to avoid puckering.
- Trim and finish the seam allowance by serging, binding, or pinking the raw edges so they don't fray inside the garment.
- After both sleeves are attached, sew the underarm seam in one continuous line from cuff to garment side seam.
Prepare the sleeve and armhole before pinning
Start by checking that your pattern pieces match your garment. The sleeve cap should fit the armhole — if your pattern is correct, the armhole measurement and sleeve cap measurement should be close (the sleeve cap is usually slightly larger to allow for shaping). If you've made changes to the garment body, you may need to adjust the sleeve length or cap height.
Press both the sleeve and the garment body with an iron before you begin. A flat, wrinkle-free surface makes pinning easier and helps you see where the seams actually are. Press the sleeve seam allowance flat, and press the armhole seam allowance flat as well. If your pattern calls for easing stitches (a line of loose stitching that gathers the sleeve cap slightly), sew those now on the sleeve piece, between the notches that mark the cap.
Mark the key points on both pieces with tailor's chalk or a fabric pen: the shoulder seam on the armhole, the underarm point on the armhole, and the top of the sleeve cap. These marks help you align the pieces correctly as you pin.
Pin the sleeve to the armhole, starting at the shoulder
Place the garment body inside-out on your work surface. Slip the sleeve inside the armhole, also inside-out, so the right sides of the fabric face each other. This is the correct orientation for sewing a seam.
Start pinning at the shoulder seam. Push a pin through both layers at the shoulder mark on the armhole and the shoulder mark on the sleeve cap. Pin straight across, perpendicular to the seam line. Move to the underarm point next and pin there. Now you have the sleeve anchored at two key spots.
Work from the shoulder toward the underarm on one side, pinning every inch or so. As you pin, gently ease the sleeve cap to fit the armhole — the sleeve should be slightly fuller than the armhole, and you're distributing that extra fabric evenly around the curve. The fabric should lie flat against the armhole without wrinkles or tucks. If you see puckering, remove the pins and redistribute the fullness. Repeat on the other side of the shoulder, working toward the other underarm point.
Sew the armhole seam with a 5/8-inch allowance
Thread your machine with thread that matches your garment. Set the stitch length to 2.0 to 2.5 millimeters — a standard length for garment seams. A slightly shorter stitch (closer to 2.0) gives you more control on the curve and less chance of puckering.
Position the sleeve under the presser foot with the garment body on top. This way you can see the armhole and watch for puckering as you sew. Start at one underarm point and sew slowly around the armhole, following the 5/8-inch seam allowance line. The 5/8-inch allowance is the standard for most garment patterns — measure from the raw edge of the fabric to your needle, and keep that distance consistent.
Sew slowly and pause every few inches to check that the fabric is feeding smoothly and the sleeve cap is not bunching. If you see a pucker forming, stop, backstitch to find the thread, and remove the pins in that area. Redistribute the fullness and re-pin, then continue sewing. Finish the seam at the other underarm point and backstitch to lock the thread.
Trim and finish the seam allowance
Remove the garment from the machine and try it on inside-out to check the fit. The sleeve should sit smoothly in the armhole without pulling or sagging. If the fit is wrong, you can carefully remove the stitches and re-sew, but most of the time the first seam is correct.
Trim the seam allowance to 1/4 inch using sharp fabric scissors or pinking shears. Pinking shears cut a zigzag edge that resists fraying and is faster than binding. If you have a serger, run the seam through it to trim and finish in one step. If you're binding the seam (a more formal finish), cut 1/2-inch bias tape, fold it over the raw edges, and stitch it down by hand or machine.
Press the finished seam allowance toward the sleeve using an iron and a pressing ham or rolled towel to maintain the curve. This helps the sleeve sit smoothly and makes the inside of the garment look neat.
Sew the underarm seam after both sleeves are attached
Once both sleeves are sewn to the armholes, close the side seams of the garment body if you haven't already. Then sew the underarm seam of each sleeve in one continuous line. This seam runs from the cuff (or sleeve hem) up through the underarm and down the side of the garment body to the hem.
Pin the underarm seam with right sides together, matching the underarm points where the sleeve meets the garment body. Sew with a 5/8-inch allowance, using the same stitch length as the armhole seam. Backstitch at both ends. Trim and finish this seam allowance the same way you finished the armhole seam.
Press the underarm seam flat, then press it to one side (usually toward the back of the garment). This seam is straight, so it's much easier to sew than the armhole and usually comes out perfect on the first try.
Troubleshoot common sleeve problems
Puckering around the sleeve cap: This happens when you sew too fast or don't ease the fullness evenly. Slow down, check that your easing stitches are holding the fabric, and redistribute any bunching before you sew. If the pucker is already sewn in, you can remove the stitches and re-sew that section.
Sleeve pulls or gaps at the armhole: The sleeve cap may be too small for the armhole, or the garment body may be too large. Check your pattern measurements against your finished garment. If the fit is off, you may need to take in the side seams or adjust the sleeve cap height on the next garment.
Sleeve hangs twisted or sits too far forward: This usually means the shoulder seam of the sleeve is not aligned with the shoulder seam of the garment body. When you pin, make sure the shoulder marks line up exactly. If the sleeve is already sewn, you can remove it and re-sew with better alignment.
Seam allowance shows on the outside: You may have sewn with the wrong sides of the fabric facing each other (outside-out instead of inside-out). Check your orientation before you pin. If this has already happened, you'll need to remove the stitches and re-sew.
Frequently Asked Questions
Do I have to sew the sleeves before the side seams?
Most patterns call for sleeves first, but you can sew side seams before sleeves if you prefer. The advantage of sleeves first is that you have more room to work and can adjust the fit more easily. Side seams first is fine if your pattern says so — just follow the order in your pattern instructions.
What if the sleeve cap is way too big for the armhole?
Check that you're using the right size pattern and that you haven't accidentally cut the wrong pieces. If the pattern is correct, you may need to add easing stitches to gather the extra fabric, or the garment may not fit you well. You can also try a different pattern designed for your measurements.
Can I sew sleeves on by hand?
Yes. Use a backstitch or whip stitch and follow the same pinning steps. Hand sewing takes longer but gives you more control on the curve. Use thread that matches your fabric and make stitches about 1/8 inch long for a strong seam.
How do I know if my sleeve length is right?
Try on the garment inside-out after you've sewn the sleeves. The sleeve should end at your wrist bone when your arm is relaxed at your side. If it's too long or too short, you can remove the cuff or hem and adjust before finishing the sleeve edge.
What's the difference between a set-in sleeve and a raglan sleeve?
A set-in sleeve (what this guide covers) has a curved cap that sits in the armhole. A raglan sleeve runs from the underarm all the way to the neckline, so it's sewn differently — the seam goes up the front and back of the garment body, not just around the armhole. Your pattern will tell you which type you're sewing.