Do You Lose Campaign Progress in Modern Warfare 2 on PS3?

No—Progress Is Saved Per Save File

Call of Duty: Modern Warfare 2 (2009) on PS3 saves campaign progress to a specific save slot on the hard drive.

How It Works

• When you start a new campaign, you choose a save slot (1–4).
• Each mission completion auto-saves to that slot.
• Quitting mid-mission saves a checkpoint; "Continue" resumes from last checkpoint.
• Starting a New Game creates a new slot—previous slots remain untouched.

Common Confusion

• Mission Select: Allows replaying any completed mission on any difficulty without overwriting progress.
• Difficulty Change: You can change difficulty mid-campaign from the pause menu; progress continues in same slot.
• Corrupted Save: Rare. Backup saves to USB (Game > Saved Data Utility) periodically.

You only "start over" if you deliberately select New Game and overwrite a slot, or delete the save file.