T-shirt Onesie — A Tutorial

I’ve been in full baby crafting gear lately. Last night I sewed a couple of little pants and I’ve been tinkering with the idea of making a onesie out of an old T-shirt. I have a special one in mind, but I thought I should test it out on a junker first. Success!

It was about a 45-minute project. And here’s how I made it:

A small adult T-shirt, or a child’s size shirt
A store-bought onesie (to use as a guide)
Velcro (the kind you have to sew on, not stick on)
Stretchy materials needle (recommended, but not required)


First, turn your T-shirt inside out and fold it in half down the middle. Fold your store-bought onesie in half down the middle and lay it on top of the T-shirt so the collars line up and the shoulders/sleeves run along the top. Cut around the onesie leaving about 1 inch of a border on the sleeves and sides but about 2.5 inches at the bottom crotch area. You should end up with one piece of fabric where the front and back are connected at the collar/shoulder/sleeve area.

Trim the sleeve edges how you prefer. The sleeves just happened to end up right where the big shirt sleeve began so there was a sewn edge that made it easy to trim.

Turn under the edges of the legs (there should be four of them) and sew in place. This looks pretty rough since I didn’t have a mini screwdriver to install my stretch needle. When you sew jersey be sure you stretch it out as you’re sewing it so there is give to the seams.

Sew along the sleeves and sides of onesie using a half-inch salvage.

Turn right-side out and turn under the bottom crotch flap of the front twice over. This will add extra thickness to better stabilize the velcro. Pin and sew in place.

Next, turn up the bottom crotch flap of the back, but just once over. You want the back flap to be about two inches longer than the front flap once the edges are turned under. Pin and sew in place.

I chose to use three squares of velcro, but a strip would work also. Sew the softer side of the velcro to the wrong side of the back flap. Sew the rougher strip of velcro to the RIGHT SIDE of the front flap.

And there ya have it — a make-your-own onesie. This would be a fun project if you had a sports team T-shirt or a TUXEDO T-shirt, which is the reason I wanted to try this out. Stay tuned for my tuxedo onesie in the next couple of weeks.

And, as always, please contact me if part of this tutorial isn’t clear.

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