Like I said before, I am excited for this tutorial! Not because it’s super awesome, but because it’s super practical and easy, and I should have thought of it sooner. Ever since B was born, I noticed that on many dresses and tops, her onesie was sticking out, either out the sleeves or around the neck. Of course she doesn’t have to wear aonesie, but I like her to wear one–even in the summer some days when her shirt flies up and reveals bare skin. Aonesie seems to have them “put together” more. Seriously, it’s been a topic of conversation more than once amongst my friends and I.
In the past, I have searched online and could only find tank top onesies that are scoop neck. And I have never seen them in any stores around where I live. That still didn’t solve the problem of when my baby wears square neck tops. I even did a recent search just to see if I was copying anyone, and hopefully, I’m not. Yea! If you’ve done it, then please know that I am completely unaware. I believe in giving full credit where it is due!
The best part? It’s super, duper easy to make them–especially since you start with a normal onesie! What you’ll need:
*a onesie
*some extra white knit, at least 13″ wide
*thread
I will be using a size 18 month onesie today.
First, cut off the top of the onesie like this:
You want to cut at a diagonal, so that the straps will stay on their shoulders. So at the top of my cut, it measured an inch over from the seam. Do not go more than an inch over, since that would defeat the purpose of the square-neck:
Measure straight edge at top. Mine was 5″.
Now place the pieces you cut apart back together, and measure from the start of your cut, to the neckline, so you’ll know how long to make the straps. Mine is 6″. You’ll need this measurement for the straps.
You want to cut at a diagonal, so that the straps will stay on their shoulders. So at the top of my cut, it measured an inch over from the seam. Do not go more than an inch over, since that would defeat the purpose of the square-neck:Measure straight edge at top. Mine was 5″.
Now place the pieces you cut apart back together, and measure from the start of your cut, to the neckline, so you’ll know how long to make the straps. Mine is 6″. You’ll need this measurement for the straps.
Now you will cut 4 straps. Two pictures above, you measured the straight edges. Mine was 5″. I added an inch (knit tends to shrink a little when sewing), and cut two 6″ x 2″ strips (these will line the top of the raw edges for the top and back). I then doubled the 6″ measured above, and added 1″ for a total of 13″. So two 13″ x 2″ strips.
**TIP: Your straps and strips will be more stretchy if you sew across the vertical lines on knit fabric. The pictures don’t show me doing that. I learned my lesson, though! Sachiko has a great explanation HERE. See trick 3.
Sorry if that got confusing just then, you need two 6″ x 2″, and two 13″ x 2″ strips.
Fold each strip in half and iron. Then fold each edge to the middle fold, on both sides and iron, like this:
Fold each strip in half and iron. Then fold each edge to the middle fold, on both sides and iron, like this:Fold those in half and iron.
You’ll have this now:
You’ll have this now:
Open up one strap and insert the top edge of the onesie on the front or back. 
Fold strip over.
Fold strip over.
Pin both strips on the front and back raw edges.
Sew, making sure to backstitch as soon as you hit all the layers that are needing to be sewn together. I just lined my edge up like this:
If you get to the end and have some excess, make sure you backstitch before passing all the layers.
Cut off excess strip.
Your onesie should look like this now:
Take one of the 13″ straps. Starting at the back corner, pin the strap around the armhole.
Your onesie should look like this now:
Take one of the 13″ straps. Starting at the back corner, pin the strap around the armhole.
Sew, starting at the back, making sure to backstitch.
You can basically just turn the fabric so you sew a straight line, even though it is a curved arm area.
You can basically just turn the fabric so you sew a straight line, even though it is a curved arm area.
Once past the other end of the armhole, keep on sewing until you have about an inch left of the strap.
Tuck the end of the strap over if you want a more finished look. Make sure your strap is turned the right way for attaching to the other side, so it’s not twisted.
Fold over. You are now back to where you started sewing the strap on.
Now you’ll have a circle! 
Repeat with other armhole. And you are finished! Wasn’t that easy?
YEA! No more onesie sticking out all over!!!
Is it there? Let’s check. Yep! 
This looks like a great tutorial. I don’t have a girl so probably won’t be using it but can I just say that your little girl is SO STINKIN’ CUTE!!! Her little picture just made my night. Maybe her and my Mikey Man should get together some day! He is 17 months! ;0)
I can’t sleep and glad I can’t because I need to tell you that you are a genius! I didn’t quite get it when you were explaining it to me last week, but now I totally do. Like a onsie cami! GENIUS!
And B is so cute. It’s true.
wow, this is soooooo great! Thanks for sharing. I love using onesies here at my house!
You need to submit this to Tip Junkie. If you don’t, I will :) I already started the form, but it asks for permission, which I don’t have authority to give. So go do it :)
What a great tutorial! I just cleaned out my daughter’s drawer and was about to give them away because she’s getting old for onesies but with this idea, I better go back and get all those out of that bag before they get thrown out! Thanks a lot!!!
Great idea!!! How do you come up with all of your ideas??? Your mind must be constantly working away…I like my kiddos to wear onsies too. Even during the summer time. I’ll have to see if I can get my machine to sew on knit….
what a great idea! Thanks for the tutorial!
I have been wanting to do this for months! I’m the exact same way. I like Syd to have a onsie on even if it is warm because it looks more “clean” or whatever. This is perfect since I’ve made some summer outfits with pilot sleeves and it loos so funny with onsie sleeves sticking out! Thank you!
Just what I was looking for! My baby has a petit bateau tank onesie that I love, but I don’t really want to spend $14 on an undershirt. I will make these for sure! Thanks for the tutorial.
Thank you for this tutorial! It’s a simple idea, but one I wouldn’t have thought of. I used it to make a tank onesie for my older daughter 3 years ago for her Easter dress and just made another today for my 2-month-old’s Christmas dress. I too like a onesie under all outfits, especially dresses. And onesies and flutter sleeves just don’t work. Thank you!!!