Isabelle One Piece Written Directions


- Isabelle One Piece PDF Pattern

- 1 yard swimwear fabric

- Matching thread

- 1/4" or 3/8" swimwear elastic

- Cutting tool like scissors or rotary cutter

- Loop turner

- Seam ripper

- Overlock machine OR zig-zag stitch on a regular sewing machine

-AND regular sewing machine

*This tutorial uses both an overlock machine and a regular machine. You will need to be able to make a straight stitch.

Printing & Assembling the Pattern

Choose either US Letter, A4, or A0 format, all of which are included inside your download links. Open up your desired file and read through the initial instruction pages for more information on how to print and assemble this pattern. Note that if you're using the A0 verison you will need to pull up either the US Letter or A4 formats in order to access the direction pages.

You will first need to choose what type of cups you plan to make- either with or without a dart. For undarted cups, you'll use Pieces 1 & 2. For darted cups, you'll use Pieces 3 & 4.

Next, choose what coverage option you will make. For cheeky, use Pieces 5 & 6. For full coverage, use pieces 7 & 8.

In total you should have 4 pattern pieces- 2 cup pieces and 2 body pieces.

Print and assemble your pattern according to the instructions inside the pattern, then you're ready to begin!


Assemble your pattern and cut your desired size.

Then, cut 2 of each pattern piece in your swimwear fabric. 1/4" seam allowance is included. If you're making your one piece with two different fabrics, cut 1 of each pattern piece in EACH fabric.

At this step you will also cut your straps, and the exact measurements are provided inside the pattern.

Step 1

First we need to attach the bust pieces into the bottom front piece. This will allow us to work with one continuous front piece.

To do this, match your like fabrics so you have a left bust, right bust, and bottom front grouped together. You should have two of these- one as your "outer" fabric and one as your "lining" fabric. Even though this is a reversible piece we will use those terms for clarity.

Match the bust pieces to the cup openings on the bottom front piece. Make sure you correctly match the left and right bust pieces and ensure right sides are together. Only a portion of the bust pieces will be sewn in, just the amount that the cup openings provide.

Because of the shape of the curve, we recommend you use lots of pins. Once you're ready, use an overlock stitch or a zig zag stitch to attach each of the bust pieces to the front bottoms. You should be sewing 4 separate seams.

Step 2

Once your bust pieces are attached we can now work with our "front" pieces and our "back" pieces.

Match fronts with fronts and backs with backs, right sides together.

For the back piece, you're going to sew AND attach elastic to the neckline, armholes, and leg holes with either an overlock stitch or zig zag stitch. For this whole tutorial we recommend sewing elastic with no tension, you want it to sew on evenly. If you prefer a more snug fit, especially on the leg holes, you may choose to stretch the elastic.

For more information on how to sew elastic, click here. 

For the front piece, sew AND attach elastic to the leg holes, arm holes, neckline, and the "belly scoop". You're also going to sew the remaining lower part of the bust cups, but do not attach elastic to these.

Take your straps and fold them in half lengthwise, right sides together. Sew along the raw edges and attach elastic too. Again, make sure you're sewing your elastic as evenly as possibly to prevent any bunching or wavy application.

Once the straps are done, take your loop turner or safety pin and turn the straps all the way to the right side.

Step 3

Now it's time to attach the front and back pieces together. To do this, take the front piece all the way to the right side. Insert it inside of the back piece, making sure right sides are together. Match up the shoulder straps, the sides, and the gussets. At this point the entire front piece should be encased inside the back piece, with nothing poking out. Make sure the connections at the sides, shoulder straps, and gussets are fully aligned and then sew across all four layers of fabric to secure them all down.

Step 4

Everything is now inside the back piece, so take a seam ripper and rip a 1-2" hole somewhere along an existing seam. Through this hole take the entire suit to the right side. Then, using a straight stitch or an invisible stitch, sew the hole closed.

Step 5

Now it's time to sew in the straps and strap channels. You can do this two different ways.

1. It may be easiest to first insert your straps inside the strap opening at the inner corner of each bust piece. Then go over to your sewing machine and sew a strap channel above the strap inside. You will use a straight stitch for this.

2. You could choose to instead sew the strap channel first, then insert your strap inside. It may help to have a loop turner to insert the strap in since it can get tight.

Regardless of what you choose, your strap channel only needs to go from the inner corner of the bust piece up to where the connection with the front bottom is. There's no need to make the channel any longer.

Step 6

Make sure your strap is fed all the way in, then use a straight stitch to tack down the strap inside the strap channel. Really make sure to get a good stitch on this, it will be holding a lot of tension when stretched!

Trim your excess threads and then you've completed the Isabelle One Piece.

Wrap your straps however you'd like, and that completes the Isabelle One Piece!