DIY: Adventure Time Finn Backpack Tutorial

Adventure Time Finn Backpack TutorialAlthough I didn’t intend on dressing up as Finn for Halloween, after I made the Finn hat, I just couldn’t stop. I mean, what’s a Finn hat without a handy Finn backpack? This minimal costume/cosplay was fun to make, fun to wear, and I can’t wait to wear it to my next con! With that, here’s a lengthy tutorial on how to make your own Finn backpack.

You will need:

  • A half a yard of light green fabric (I recommend using fleece)
  • A half a yard of dark green or medium green fabric
  • Large green button
  • Estimated time: about 2-3 hours
Let’s get started!
Double up the light green fabric and cut a 13.5″ x 9.5″ rectangle. Round the edges on two of the corners. Double up the darker green fabric and cut  a 13.5 x 11.5″ rectangle. Round the edges on two of the corners. You will end up with 4 pieces like this.
Finn Backpack TutorialTake one of the light green pieces and fold the edge and sew it down. Remember to only sew the light green piece. You are not sewing the light and dark green pieces together for the front since we will have a functional button. The button will eventually go through this part of the backpack.
Finn Backpack TutorialFinn Backpack Tutorial
Pin the two pieces together. Note that the light green piece will need to overlap on top of the darker piece so that you can have a functional button. Now take your other two green pieces and pin those together strategically so that they match the front pieces in size and proportion.
Finn Backpack TutorialFinn Backpack Tutorial
Now cut one strip of light green fabric about 27″ x 3″. This will be used as an edge of the backpack body. Then cut one strip of darker green fabric about 28″ x 3″. This will also be used as an edge of the backpack body. Sew those together on one edge.

Fin backpack tutorial

Match the part where the light and dark green meet to the same place where they meet on the front part of the bag. Start pinning from here and go all the way around the bag. When you reach the opposite end, pin and sew the other end of the strips together and make sure the part where the light/green colors meet all match up. Sew all the way around the edge of the oval shape.Fin backpack tutorialFin backpack tutorialFin backpack tutorialYou should end up with something like this.
Fin backpack tutorial

Before you sew on the other side of the backpack, you’ll want to sew the straps on it first. To do this, cut two light green strips 12″ x 5″ and two dark green strips 12″ x 5″. Sew each light green strip to the dark green strip. Fold in half the long way and sew it closed. Then flip them inside out. You should end up with two of these suckers.

Finn Backpack Tutorial

Now pin them to the right side of the back piece of the backpack. I decided to fold the ends of each strap so that it had a clean edge. Once pinned on the back piece, make sure to try them on to make sure they are positioned properly. Once they’re pinned down, sew a small rectangle to hold them in place. This part is optional, but I reinforced the straps with a zig-zag stitch as well.

Finn Backpack Tutorial

Finn Backpack TutorialFinn Backpack TutorialFinn Backpack Tutorial

Now you’re ready to pin everything together! Make sure all the edges line up correctly!

Finn Backpack TutorialFlip inside out using the front opening and position your button. Sew this on the darker green park and cut a small hole for the button to go through on the light green piece.
Finn Backpack TutorialAlgebraic!! You’re done!
Finn Backpack Tutorial

Now you can stuff it with clothes, pillows or whatever other goodies you want!

Finn Backpack Tutorial

Happy adventuring!

51 thoughts on “DIY: Adventure Time Finn Backpack Tutorial

  1. Omigosh!! This is totally mathematical! I’ve been looking for a pattern that makes sense for ages! I’m making a Fiona costume and I needed the backpack pattern. Thank you so much! I can’t wait to get started on mine!! :D

    • It’s made of fleece, so I wouldn’t recommend putting anything too heavy in it. Maybe you could alter it by using a thicker fabric or adding support to the base?

  2. I just made his backpack for my 11 year old granddaughter for Halloween! Your instructing were clear and it took less than 3 hours! And I haven’t sewn in years!!! I even added a sheath between the straps on the back for her sword. Thank you soooo much! She is happy, happy, happy. Hasn’t taken it off for hours!!!

  3. Hey ,like Kayln, I wanted to be using this mathematical pack for school. What kind of material would you recommend?

  4. It would be more helpful to have exact measurements for this backpack (e.g. how much of an edge do you leave on the light green flap for the button, and how much of an edge for the edges and straps of the backpack). Also, the part where you line up the light and dark green pieces gets confusing…maybe change the wording and add in where/when/how much you sew the light/dark green pieces together for the back of the backpack. I like this pattern the best for Finns backpack but I highly recommend making the instructions more user-friendly for new seamstresses.

    Thanks for the instructions.

  5. My 13 year old son is dressing as Finn for Halloween and had to have the backpack – of course! We already had the hat, so I started looking around for a DIY pattern. Yours was easy to follow, and in one afternoon I have a happy son and an awesome backpack! And best of all, the fleece was on sale and I already had thread and a button so it cost less than $4. Thank you!

  6. Thank you for your clear and easy instructions! After googling tons of other tutorials, yours was the clearest and easiest to follow. I made one for my daughter this afternoon for her Fionna costume.

  7. I just made this and it turned out perfect! I seriously can’t believe how good it looks, especially since it’s functional. You’ve help make my Fionna dreams come true. Thanks!

  8. Great tutorial–thank you for helping me earn the admiration and appreciation of my 12-year-old Finn!! I ran out last night and bought the fabric, and with your great directions and detailed pictures, was able to whip up the backpack this afternoon. Thank you!

  9. Your instructions were amazing, other tutorials I was trying were so unclear. Thank you so much :D now my Fionna costume is complete!

  10. Thanks for the tutorial. I made a backpack for my 9 year old son. It was easy with your instructions. He was soooo happy when I finished it. He was able to dress up for school, so he went as Finn, and he received many compliments for the backpack. Thanks once again!

  11. Hey Emilyo, it’s Jake again. I made my backpack and it’s totes math but there’s a problem. Since I am using it for school (It works great) I used interface and doubled up the fleece. Instead of using a button for the opening I used an invisible zipper.(The button opening would have stretched overtime) Something that isn’t so math is the zipper. It gets stuck a lot because of the thickness of the fabric. I was hoping that you could suggest a way to fix my prob.

    • It’s probably getting stuck b/c it’s an invisible zipper. I would suggest replacing it with one of those thicker plastic ones. It will be visible, but probably save you the hassle of it getting stuck. Good luck!

  12. Loving the pattern! All my friends are anime mad so this will make great Christmas presents for them all. Shame I didn’t see the pattern before comic con London but Im sure they will all love them and wear them for comic con in may, which I will also be going to. Any suggestions to how I could personalise each one so they all have unique bags?

  13. This really is mathematical. Some friends and I are dressing as the Adventure Time cast for Halloween and I wanted my brother to be Finn. I went searching for a ton of DIY instructions for the backpack and yours was by far the best. Thanks for posting the tutorial.

  14. Thank you so much for this tutorial! I am cosplaying Finn during a convention in two months, so this comes in really handy. :)

  15. Thank you so much. I am not a sewer and I have managed to hand sew this whole thing. My son is going as Finn to a book week dress up this week.

  16. I had zero experience in sewing but I made Finn’s backpack with ease thanks to this tutorial! I hand-stitched it since I’m not really good at stitching curves with a sewing machine… The backpack turned out beautiful just the same and fits perfectly! Thank you for helping me perfect my Fionna cosplay :D

  17. Hi, I love this idea and I think it’s algebraic! But I’m just wondering, the measurements you put for each one, do we cut exactly those or add an extra centimetre of seamline?

  18. So I was super excited about this when I found it, but despite triple checking my measurements, it still ended up being extremely long and narrow after I constructed and sewed it together. Before I started sewing I had a feeling this would be too long, so I even trimmed it by about 3 inches. The only difference is that since I was using a thinner flanel-like fabric instead of fleece because I had about a day to make this and didn’t have time to go to an actual fabric store, so I was working with what WalMart had. Not the best materials, but it shouldn’t have altered the results THAT much…should it? The only reason I ask is because I plan on making a better one in the future with better materials, and I want to make sure I did everything I could.

    All in all though, still a good tutorial. I will say I had to spend a few minutes deciphering the instructions, but once I got it figured out it took less than 3 hours to sew. Thanks!

  19. We just made this today. Realatively easy. We have very little sewing experience and was able to make this in a couple hours

  20. Great tutorial! I found this very very helpful since my girlfriend is a big fan of Adventure Time and I was thinking of something to give her for Christmas. I though of giving her a Jake stuffed toy but I think it’s too cliche and there would be less effort :3 Soooooooo I googled for an alternative and luckily I found your website :))

    Sooo thanks a lot for helping me make my girlfriend happy this Christmas :))

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