Unlike the other Square Enix Marvel title, Avengers, the new Guardians of the Galaxy game doesn't have an in-game store to buy cosmetic items. Instead, they're all unlocked through the course of playing the game, and even the ones given as a bonus to pre-order customers aren't exclusive to folks who handed over their money early.
You'll encounter most of the outfits fairly easily just by playing through the game, likewise, some are rewarded when you hit certain points. There will be some spoilers below. Though none will contain any details on the storyline, some will give away locations. We'll keep details as vague as possible though so as not to ruin any of the details.
Warnings heeded, here's how to get your hands on all the sweet threads in Guardians of the Galaxy.
How to unlock all outfits in Guardians of the Galaxy
This list will be broken down by chapter so as to make navigating spoilers a little easier. Some chapters contain multiple outfits, and you'll always be able to identify them by the glowing pink box.
They'll also show up on Star-Lord's visor as a yellow outlined object, so if you see a small yellow outline of a box, you're probably close. The levels are fairly linear, with only a small number of branching paths, so the easiest thing to do is to progress through the missions until you come to the areas in the screenshots attached to each outfit.
Players who pre-ordered the game will get early access to the Throwback Guardians outfit pack, which contains one outfit for each character. However, this is merely early access to these cosmetics, and everyone else can earn them by playing the game and finding the boxes in their respective hiding places. If you get them through pre-ordering, obviously they won't be obtainable in-game. If you didn't pre-order, you'll find their hiding places in the list below.
Golden Guardians outfits
One of the best-looking outfit sets in the game is the "Golden Guardians" set, and you'll be awarded these upon beginning chapter 14 of the game. There are no boxes to locate.
Rocket: Guardians of the Galaxy (2014)
Early into the mission, you'll come to a junction and Rocket will tell you that way is a dead end. While he leads Groot through the small opening on the left, you should head towards the route that looks like bones. When you get onto it, immediately turn to the right and you'll see a ledge to jump down to. Once you jump down, turn to the right and you'll see the box in the corner containing Rocket's MCU outfit.
Groot: Guardians of the Galaxy (2014)
When you get to a point in the mission that you're 'inside' (you'll know because it's dark and much less pink), progress until you see this pink blockage with a small hole in the bottom. Head towards it and you'll crouch down and go through the hole. The outfit box for Groot's Guardians of the Galaxy MCU outfit is inside.
Chapter 2 is one of the shortest in the game but it still has some secrets to find. When you're walking through the bowels of the ship you'll get to a point where you have to help Cadet Gold block some flames by pushing a box across them. As you move forward, she will go right but straight in front of you is a small cut-through. Go straight forward and through it, follow the path, and you'll find the outfit box for Star-Lord's Nova Corps outfit.
Gamora: Guardians of the Galaxy (2014)
The first outfit on this mission to find is Gamora's MCU suit and it's probably one of the harder ones to locate. As you progress through the mission, you'll come to a forest-like area and see a red structure overhead. You'll have an interaction with Gamora while she's looking at tracks on the ground. Turn right here, follow the path to the end, and then turn left. Head through the small opening into a cave.
In the back right corner, destroy the gunk and head through another small opening. You'll now have to defeat some of the jelly cube creatures, but once despatched clear one final opening and climb up to claim the outfit.
Groot: Five Horsemen of the Apocalypse
You'll find the Groot Five Horsemen of the Apocalypse outfit overlooking the arena where you fight the two creatures and acquire the cage. Follow the mission path but once you get Groot to provide a bridge, head left instead of following the mission path to the right. Use the element gun to freeze the geyser and use it to ascend to the upper tier and open the box.
Drax: Guardians of the Galaxy (2014)
As you're first escaping through the bowels of Lady Hellbender's fortress, you'll come to this location after avoiding the first death drone where your mission path will go through the door on the left. Instead, go straight and a side area will become visible. Drop down and traverse the area, and at the very end is the box for the Drax MCU outfit. It should be noted this location could be linked to who you decide to sell to Lady Hellbender. This location was after choosing Rocket.
Rocket: Five Horsemen of the Apocalypse
When escaping through the sewers there's an easy outfit to find. The mission path will bring you to a fork, with the rest of the Guardians going right. Turn and go the other way and tucked up against a blocked path you'll find the box for Rocket's Five Horsemen of the Apocalypse outfit.
Drax: Nova Corps
Early on when you find yourself in the room where you have to re-route the power to unlock the door, there is a second door to unlock. Using Star-Lord's visor, direct the power to the left-hand door, which will open and give access to a bathroom. Just inside the door on the left, you will find the box containing the Nova Corps outfit for Drax.
Groot: Nova Corps
Further on in the chapter, you'll come to a room where you have to climb up what looks a bit like a scissor lift. Instead, head towards the back of the room, and then hiding behind some boxes on the right-hand side you'll find the Groot Nova Corps outfit.
Star-Lord: Guardians of the Galaxy (2014)
In the central area of Knowhere after Mantlo's Bar and after you've been separated from the rest of the team, you'll be able to locate Star-Lord's MCU outfit. It's important to get it this time around as when you come back to Knowhere later on you'll see it but won't be able to get to it.
When you see the structure with the upper deck and a staircase to the left, you need to aim between the two. There's a cut-through onto some red pipes. Hop the barrier onto the pipes, turn left, and follow it to the outfit box.
Rocket: Nova Corps
When trying to remove the clamps for the second time on the big Nova Corps power, er, thing, you'll go into two rooms to rectify the problem. Inside one, use Star-Lord's visor to help redirect power from the electrical switch to the small door on the right. Once it opens, go inside and claim the box and with it the Rocket Nova Corps outfit.
Gamora: Nova Corps
One of the outfits you can acquire in chapter 7 you may have already seen in chapter 2 when walking through the ship with Nikki. You come to the same staircase you went down with her, with water flooding the very bottom of it. Head to the very bottom and you'll find a switch on the wall to turn off the electricity with Star-Lord's element gun.
Next, direct Gamora to cut through the vertical pipes in the corner, then squeeze through and find the box containing the Gamora Nova Corps outfit.
When escaping from Raker you'll come across a pool of red liquid where you have to escape down a drain. As you reach the bottom of the slope, there is a large box to the right. Get Drax to move it and place it over the gap you just emerged from. Climb the box, jump over the ledge, and as you drop down the outfit box will be in front of you.
Drax: Cage Match
When you come to this room with the large circular drop in the middle surrounded by a walkway, go to the direct opposite side to the door. Here you'll find the box containing the Drax Cage Match outfit.
Gamora: Five Horsemen of the Apocalypse
When you first enter the cave and come to the river you have to cross with a waterfall to your right, head straight through the waterfall. On the other side and off to the left is the outfit box for Gamora's Five Horsemen of the Apocalypse outfit.
Rocket: Hero of Halfworld
As you emerge from a small cave there will be a ledge on the right-hand side. Jump up onto this and go straight ahead and cross the walkway where you'll be edging along a rock face. As you come to the other side, the box for the Rocket Halfworld outfit will be right in front of you.
Groot: Annihilation - Conquest
As you come into the part of the chapter where Groot is lighting the way, it's a little less obvious where the cut-through to the next outfit box is. As you advance, the mission path will take you off left but ahead a little and on the right is a small gap in the rocks with plants growing around it. Squeeze through here and the outfit box is in the clearing.
Drax: Thanos Imperative
The first outfit of this chapter can be found towards the beginning. Jump up onto the right-hand structure (once you've dispatched the enemies) and then jump the gap to the other structure to open the box.
Rocket: The Smuggler
As you walk through the now ruined Knowhere marketplace you will come to this location where your mission path will take you off to the left. Keep going straight ahead and on the right there will be a blockage to clear with the wind element. The Smugger outfit for Rocket is waiting just behind.
Gamora: Casual Kill
As you cross the bridge by traversing the rooftops you eventually come to a point where Drax has to break a hole in the floor to proceed. When you slide down the newly created ramp, turn around and you'll see a small opening to crawl through. Go through here and you'll find the box for Gamora's Casual Kill outfit.
After clearing out the enemies on the giant, white, celestial brain donut, you'll get Drax to move a large box to enable you to progress. Once you climb up to the gantry, at the end there is a panel that Gamora can jump up and anchor on in order to throw you up to a higher platform. At the end of this platform is the box for the Apocalypse-Lord outfit.
Groot: Five o Clock Sprouts
As you cross the narrow ledge pressed up against the wall, you'll come to a small opening in the mountain. You'll need to go left to carry on the mission, but around the corner to the right is the outfit box.
Rocket: The Stinger
After unlocking the plasma element for Star-Lord's blasters you'll come across a space full of alien plants that you'll want to destroy. Over in the far right-hand corner of this space, you'll find two plants close together. Burn these away and behind them, you'll now be able to get at the box for Rocket's Stinger outfit.
Gamora: Black Vortex
In the later part of the chapter, look out for this flat surface, which you can deploy Gamora to in order to propel yourself up to an otherwise impossible-to-reach ledge. From here, jump across to the adjacent ledge to unlock the Black Vortex outfit for Gamora.
Drax: Katathian Monk
As you progress after the snowy field of death plants you'll come across a ramp with one of the same plants at its base. Go up the ramp towards the blue icy wall and you'll find an outfit box waiting for you.
Inside the wind tunnel, you'll find an outfit box on the upper platform at the very end. To reach it you'll need to first reach the end by using the wind element on Star-Lords blasters to raise the blockades to hide behind until the wind stops. When you reach the end, you'll need to quickly jump up onto the raised platform on your left and pull up the blockade to avoid being blown away. When the wind stops again jump across to the other platform and open the box.