Team Fortress 2 System Requirements for Mac OS X

MINIMUM:
OS: OS X version Leopard 10.5.8 and above
Processor: 1.7 GHz Processor or better
Memory: 1 GB RAM
Graphics: NVIDIA GeForce 8 or higher, ATI X1600 or higher, Intel HD 3000 or higher
Network: Broadband Internet connection
Storage: 15 GB available space
Additional Notes: Mouse, Keyboard

Requirements for Windows click here