Here is the full list of all 37 Psychonauts achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Achieve Rank 101.
Find all Golden Helmets.
Spy on Bobby's love life.
Hear Vernon's Ghost Story.
Cook and consume two different kinds of roast in one sitting.
Witness Maloof's transformation.
Discover the secret history of Whispering Rock.
Gather all Figments.
Revisit all brains after completion.
Buy an item from the Camp Store on Christmas.
Sort all Emotional Baggage.
Crack all Vaults.
Find Edgar's Secret Garden.
Uncover Milla's Secret.
Complete the Punchy Target mini-game.
Complete Meat Circus.
Achieve Rank 80.
Complete The Asylum.
Introduce all Camp Kids to Mr. Pokeylope.
Give the Coach's speech on the stump.
Read many bulletin board messages.
See yourself through the eyes of many others.
Re-brain the Children.
Redeem all 16 Scavenger Hunt Items.
Complete Waterloo World.
Complete Black Velvetopia.
Earn all Merit Badges.
Achieve Rank 60.
Complete Gloria’s Theater.
Use the bacon. A lot.
Complete The Milkman Conspiracy.
Achieve Rank 40.
Complete Lungfishopolis.
Complete Milla’s Dance Party.
Achieve Rank 20.
Complete Sasha’s Shooting Gallery.
Complete Basic Braining.