• Number of achievements: 57
  
• Number of missable achievements: 1 (I'm always here for you, darling!)
  
• Minimum Playthroughs: 1
  
• Free-Roam After Story: Yes
  
• Does difficulty affect achievements?: No

Since the game is nonlinear and achievements can be unlocked in any order I didn't set them chronologically according to my own playthrough. Instead I grouped them in various categories.

There is only one missable achievement in the game and it can be unlocked very early (right after the tutorial area) and after that you're free to explore the game the way you want without worrying about missing anything. Every area remains accessible, all items can be picked up.

Achievement "Duck, Duck, Goose" might get more difficult to obtain after a certain point in the game. I'd recommend trying to get it as soon as you start seeing Panic Attacks in Nick's brain. During my playthrough Panic Attacks stopped splitting into multiple copies later in the game when encountered in other areas.

Achievement "Nest Egg" requires you to upgrade your PSI wallet twice and then fill it completely with PSI. If you want to reduce the amount of grind after the story to unlock it you might consider reducing your spending to a minimum. Personally the only things I bought were Cores to level up, wallet upgrades and two pins at levels 50 and 52 to reduce prices at the store by 50% and increase PSI drops. This allowed me to unlock this achievement shortly after reaching the final area of the game (GreenGreen Needle Gulch). However I accumulated further 2800 PSI during collectibles clean-up after the story, so it's not really necessary to avoid spending completely.

I'd suggest to not bother too much about finding all available collectible items during your first visit in an area. You'll have to revisit most areas anyway since some items require certain skills from later part of the game or appear only on subsequent visits.

I'm always here for you, darling!
Talk to Milla in her Office


You can unlock it right after arriving to Motherlobe. Go to the Agents atrium, enter Milla's office and talk to her.



Duck, Duck, Goose
Find the real Panic Attack during his Phantom attack


I'm not sure if this is a truly missable achievement, but it can get very difficult to obtain at some point, especially after completing the story.

While in "PSI King's Sensorium" (after giving Nick a new brain) you'll encounter a new enemy called Panic Attack. One of its attacks is called "Phantom Attack" in which he splits into five clones, four of which are fake. You need to hit the real one before they disappear. To make it easier lock on the enemy before it splits and then spam your PSI Blast. If you struggle you can use "Time Bubble" to slow it down and have more time to locate the real Panic Atack.

Side note: even though Panic Attacks keep appear in other areas of the game they seem to very rarely use the "Phantom Attack", at least that's how it was during my playthrough. I'd suggest to get this achievement in "PSI King's Sensorium" as it might be a bit difficult later.

Note.[/b] This might not be missable anymore. As per the latest update "Bonus Psychoseismometer unlocked in Otto's lab after finishing Gisu's quest" so you might be able to encounter Panic Attacks after the story.

Core Strength
Combine PSI Cards with a PSI Core at the Otto-Matic


After arriving to Motherlobe and going up the lift head to the Otto-Matic. You'll receive a free PSI Core and nine cards as part of the tutorial. Combine them to unlock this achievement.



Associate Intern
Achieve Rank 2


Self explanatory. You'll unlock this automatically with the previous achievement.


Junior Intern
Achieve Rank 10


Self explanatory.


Senior Intern
Achieve Rank 50


Self explanatory.


Principal Intern
Achieve Rank 100


Self explanatory. You'll get it most likely post story during the collectible items clean-up. I completed the story on rank 92.


Extra Credit
Upgrade your first Badge


As you rank up you gain points to spend on upgrading your badges. Simply upgrade one. This achievement was slightly bugged for me: it didn't unlock for me after levelling up my first badge, it worked fine on the second one.
After arriving to Motherlobe and going up the lift head to the Otto-Matic. You'll get your first point at as part of the tutorial and levelling up to rank 2.


Power Play
Fully upgrade a Badge


Upgrade any badge to rank 4.


Unlimited Power!
Acquire all Upgrades


Upgrade all badges to rank 4. You need to be level 102 to do that and that requires finding all collectible items in the game.


Pin Drop
Equip your first Pin


After arriving to Motherlobe and going up the lift head to the Otto-Matic. You'll get your first pin for free as part of the tutorial. Equip it to unlock this achievement.


Pinhead
Equip 3 Pins at once


Equip any three pins. In my playthrough I waited until rank 52 and bought VIP Discount Pin and Double PSI Drops Pin to get to 5000 PSI easier for another achievement.



Kingpin
Purchase all Pins


Purchase all pins from the store. It should be easy after accumulating 5000 PSI in your wallet.


PSI Roller
Upgrade to the Astral Wallet


Upgrade your PSI Wallet twice: Psifold wallet (75 PSI) and Astral Wallet (750 PSI)



Nest Egg
Completely fill your Astral Wallet


Have 5000 PSI in your wallet. It's fairly easy to achieve if you don't buy any pins you don't need. I suggest buying VIP Discount Pin and Double PSI Drops Pin when you can to reach the limit faster.


King of Pop
Max out your PSI Pop capacity


Purchase two upgrades to your PSI Pop: Mind's Eyelets and Expandolier



Fluff Nutter
Max out your Dream Fluff capacity


Purchase two upgrades to your Dream Fluff: Fluff Pockets and Jumbo Fluff Pouch


You Otto be in Pictures
Purchase all Otto Shot Filters


Purchase all five photo filters from the store. They become available after you receive a camera from Otto.

TK-O
TK throw an object to stun an enemy


Use telekinesis to pick up any object and throw it at an enemy to stun it. You can get it anywhere in the game and probably unlock it automatically in the first area.



Shared Regret
Throw a Regret's anvil at another enemy


Regrets are flying enemies carrying an anvil. Use telekinesis to get an an anvil from a Regret and throw it at another enemy. This can be easily unlocked in the first area of the game (Loboto's Labyrinth).



Pyromania
Pyro 3 enemies at once


Use Pyrokinesis to burn three enemies at once. You can get it anywhere in the game and it becomes very easy with fully upgraded Pyrokinesis.



Duck, Duck, Goose
Find the real Panic Attack during his Phantom attack


While in "PSI King's Sensorium" (after giving Nick a new brain) you'll encounter a new enemy called Panic Attack. One of its attacks is called "Phantom Attack" in which he splits into five clones, four of which are fake. You need to hit the real one before they disappear. To make it easier lock on the enemy before it splits and then spam your PSI Blast. If you struggle you can use "Time Bubble" to slow it down and have more time to locate the real Panic Atack.

Side note: even though Panic Attacks keep appear in other areas of the game they seem to very rarely use the "Phantom Attack", at least that's how it was during my playthrough. I'd suggest to get this achievement in "PSI King's Sensorium" as it might be a bit difficult later.



Objection!
Throw a Judge's gavel back at him


Judges first appear during Compton's Cookout. Use Telekinesis to get a gavel from a Judge and throw it back at him.



Take a Lickin'
Consume a PSI Pop to restore some mental energy


You should get your first PSI Pop from an enemy in Loboto's Labyrinth. You can also buy them at any Otto-Matic. Simply use one when you lose some health.



Hiccup in the Giddyup
Recover your mental energy with a Dream Fluff


You can buy a Dream Fluff at any Otto-Mattic. If you've got it in your inventory and die in combat you'll be automatically revived and unlock this achievement.

Family is in Tents
Help Dion Setup Aquatodome


After arriving to Questionable Area talk to your mother Donatella at the Family Camp, then to your brother Dion in the carpark, climb the poles to the top and use your PSI Blast to release the rope.


Good Vibes Only
Complete Gisu's Psychoseismometer Quest


Talk to Gisu in the tree house at the Quarry to receive this quest. There are three Psychoseismometers in total:

• in a cave behind Family Camp in the Questionable Area
  
• up in the trees above the car park in the Questionable Area
  
• in a cave in the Quarry

Activating each device will transport you to an area where you'll have to defeat a few waves of enemies.


Dance, Baby, Dance
Complete Queepie Quest


After arriving to Questionable Area talk to your mother Donatella at the Family Camp to activate this quest. You'll have to find your little brother Queepie six times:
1. Close to the Chaotic Watermill
2. At the end of the Sassclops Cave
3. Up in the trees above the entrance to the Questionable Area
4. Up in the trees above the toilets
5. On the roof of the Lumberstack Diner
6. In the trees above the Family Camp
Every time you're near Queepie you'll hear some music from his radio


A Fungus Among Us
Complete Lili's Request


Talk to Lili in the Quarry to receive the quest. The Fungus is in Questionable Area in a cave behind the waterfall. Slow down a log, jump on it and travel up. Jump into the cave when you see the entrance and approach the big mushroom in the middle.


Keep Your Shirt On
Scavenge all MISSION CRITICAL PSYCHONAUTS ASSETS


Talk to Norma in the Mothelobe to receive this quest. There are 16 items scattered around the world which you need to find:

Motherlobe:

• Deck of Cards
  
• Enemy Surveillance Device
  
• Psychonauts Name Plague
  
• Day Old Sushi
  
• Astronaut Ice Cream

The Quarry:

• Psitanium Knife
  
• Agent Orientation Lasserdisc
  
• Unexploded Bomb

Questionable Area:

• Novelty Mug
  
• Human Skull
  
• Switchblade Hatchet
  
• Can of Corn

Green Needle Gulch:

• Mini Murder Bug Bot
  
• Viking Helmet
  
• Beehive Shaped like My Phone
  
• Signed Copy of Mindswarm

There's already a good guide for finding these items, so I'm just going to link it instead of duplicating the same information:

https://steamproxy.net/sharedfiles/filedetails/?id=2585043202

Shutterbug
Take a photo with the Otto Shot


The Quarry. After talking to Otto in his lab you'll receive a camera. Simply use it to take a photo anywhere.



Fine Tuning
Tune in to a Stray Thought


The Quarry. After talking to Otto in his lab you'll receive the Stray Thought Tuner. After leaving Otto's lab equip it and approach a car parked nearby.



Forgot My Keys
Revisit a brain through the Collective Unconscious


Motherlobe. After coming back from the casino Sasha will take you to the Collective Unconscious. Simply enter a previously visited brain, e.g. Loboto's Labyrinth to unlock this achievement.



Home Run
Find the Family Camp


Questionable Area. Go to the Campgrounds following the signs.



Make It Stop!
Hidden achievement: Break all 3 Gramaphones in Fatherland Follies


Fatherland Follies. While in Nick's brain you'll be hearing Grulovian music. Find a gramophone nearby and destroy it for the music to stop. Do it three times to unlock the achievement. Location of the gramophones:

• "The Fall of Grulovia": door with a red light above in a tower-like building
  
• "Life In Exile": door behind Maligula's statue
  
• "Infiltrating the Psychonauts": hidden door on the right side of the tunnel inside the giant tree trunk

Safecracker
Crack all Vaults



You're it!
Tag all Emotional Baggage



Figheaded
Find all Figments


There's too many collectibles to describe their location conveniently in text format, so I suggest you check a video collectibles guide:

https://steamproxy.net/sharedfiles/filedetails/?id=2587516426

Employee of the Year!
Navigate Loboto's Labyrinth


Complete Loboto's brain.


Mentee Fresh
Receive your first assignment


Talk to Hollis Forsythe after arriving to Motherlobe.


EVERYBODY Hates Socks with Sandals
Make a connection in Hollis' Classroom


Complete the first version of Hollis' brain (Hollis' Classroom)


Know When to Fold'em
Shut Down the Luctopus


Beat the final boss of the second version of Hollis' brain (Hollis' Hot Streak).


High Roller Revelations
Cool Hollis' Hot Streak


Complete the second version of Hollis' brain (Hollis' Hot Streak).


Jung at Heart
Visit the Collective Unconscious


After arriving back to Motherlobe from the casino Sasha will show you the Brain Tumbler.


Feast of the Senses
Complete PSI King's Sensorium


Complete Nick Johnsmith's brain.


To the Letter
Deliver Cruller's Correspondence


Complete Mailman Ford's brain.


A Little Off the Top
Treat Ford's Follicles


Complete Barber Ford's brain.


Perfect Game
Bowl Strike City


Complete Bowling Ford's brain.


Sane in the Membrane
Repair Ford Fractured


Automatic unlock. Complete all three Ford's brains.


Ram It Down
Plate Compton's Cookoff


Complete Compton Boole's brain.


Buried Memories
Raid the Tomb of the Sharkophagus


Complete Tomb of the Sharkophagus


The Relic Room
Discover the Astralathe


After arriving to Green Needle Gulch go the Heptadome in the middle.


Archetypal Victory
Peruse Cassie's Collection


Complete Cassie O'Peia's brain.


Bob's Your Uncle
Empty Bob's Bottles


Complete Bob Zapotto's brain.


Tattered Family
Soothe Lucrecia's Lament


Complete Lucrecia Mux's brain.


Deluginist Darkness
Frequent Fatherland Follies


Complete Gristol Malik's brain.


Finish What Was Started
Dissolve the Deluge of Grulovia


Beat the final boss.


Making Peace
Return to where it all started


After completing the story go to the "Green Needle Gulch" and talk to Nona. This might be bugged a bit, if it doesn't unlock for you go to the "Questionable Area" and talk to your father first, then talk to Nona again.