At a glance
Call of Duty: Modern Warfare 2 (2009) has a Mac version: Steam sells it for macOS. The Mac requirements list only Intel: on Apple Silicon Rosetta 2 runs it, and old Mac versions sometimes do not start on current macOS. Try it in Steam for Mac first.
Call of Duty: Modern Warfare 2 (2009) came out on Steam on 11 November 2009, made by Infinity Ward.
What your Mac needs
The Mac requirements list only Intel.
Minimum macOS in the Steam requirements: 10.12.
Steam requirements list at least 4 GB of memory for Call of Duty: Modern Warfare 2 (2009).
Allow about 13 GB of disk space for the Mac version.
How to play
Open Steam for Mac and install Call of Duty: Modern Warfare 2 (2009) as usual.
If the Mac version will not start, you can install the Windows version through Uncork: download Uncork, sign in to Steam and install Call of Duty: Modern Warfare 2 (2009) from there (12 GB). We have not tested it ourselves.
The Windows version through Uncork needs a Mac with Apple Silicon (M1 or newer).
Call of Duty: Modern Warfare 2 (2009) uses DirectX 9.0c: Uncork renders it with its built-in graphics.