How to Alter a Blouse. Alter a blouse to fit like custom-made clothing. It's a bummer when you have an almost-perfect shirt to go with a pair of fabulous pants. Follow a couple of basic sewing rules to personally tailor your wardrobe for the perfect fit every time.
Decide what alterations are needed. On a shirt, it's easy to tell when the body or sleeves are too long or another part of the garment is too wide.
Look for seams before beginning to alter clothing. Search for pleats. A blouse can have pleats on the side or back. A shirt with straps that are too long can be altered at the back seam to shorten straps.
Get out the iron, pins and needles. Iron creases into the fabric where you need to pin the shirt together. Work on each side evenly. Take an inch off the blouse by stitching a half inch on each side.
Double check your edges. Check to see that pins line up correctly at the top and bottom of the area where the new seam is placed.
Start to sew. Use a sewing machine for bigger alteration projects. Small detail work like shortening straps on a shirt or moving a button on a blouse can be completed by hand stitching.