Board Thread:General Discussion/@comment-166.137.88.23-20130610185107/@comment-1504072-20130629162544

Soul reaper wrote:

I don't recall his age being mentioned in MGS3 but I know it was in Peace Walker.

It wasn't mentioned in MGS3, I believe Kojima once said that Big Boss was a similar age in that game to Solid Snake's age in MGS1. Even with the retcon, 29 years old vs. 33 is similar enough.