When you think of a kimono sleeve, you might imagine a traditional Japanese dress with long, straight sleeves. But a kimono sleeve is also a fashion term. It refers to a sleeve that is an extension of the bodice, not a separate piece. A finished garment with a kimono sleeve has no seam around the shoulder and underarm. The top seam on a kimono sleeve runs from the neckline down to the cuff of the sleeve. The bottom seam is a continuation of the side seam to the sleeve cuff. To make a kimono sleeve, you must begin with the pattern. You can't change a sleeve to a kimono sleeve once you have cut the fabric.
Tape the bodice front pattern to a piece of tracing paper. Make sure there is enough tracing paper to make the sleeve as long as you want it.
Draw a line at a 90-degree angle to the side seam and extend it out onto the tracing paper. Extend the line as long as you want your sleeve to be, plus extra for the sleeve hem.
Draw a line that extends from the neckline of the bodice front and runs parallel to the first line you drew. Draw a line to connect the ends of the two lines together.
Repeat steps 1-3 for the bodice back pattern. Cut the excess tracing paper from the pattern pieces. Place the pattern pieces onto the fabric cut the fabric pieces.
Pin the front and back of the fabric pieces, right sides together. Sew from the neckline out to the end of the sleeve. Sew from the bottom of the side seam up and around the underarm and to the end of the bottom of the sleeve. Hem the end of the sleeve. Repeat this step for the other sleeve.
Reinforce the seam at the underarm by sewing an extra row of stitches or sewing bias tape in the seam allowances.