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