PSI Cards are collectibles scattered all around the real world in Psychonauts, from Whispering Rock to the Upper Floors of Thorney Towers. Gathering nine of them and combining them with a PSI Core (available at the Camp store in the Main Lodge) at the bottom of the main room in Ford's Sanctuary grants Razputin a PSI Challenge Marker, which in turn increases the players PSI Cadet Rank by one. These items can also be redeemed by the Fortune Teller.
- Judging from the symbols on the front, PSI Cards appear to be real life Zener Cards, cards used to conduct experiments on extra-sensory perception (Clairvoyance).
- Loose PSI Cards always have a star symbol on the front, but the ones floating around PSI Challenge Markers have various designs.
- There are 117 cards floating around the game world.