The 48-year-old actor was just a few points short of being able to graduate with his classmates at Santa Monica High School in 1983, so his parents urged him to stay behind to earn the extra credits.
Sheen decided to embark on a Hollywood career instead, but says he has always wanted to complete what he started more than 30 years ago, reported TMZ online.
"It was a loose end that always bothered me. I just have this lifelong habit of never finishing things. The idea my parents had was for me go to summer school. My response was: 'There's school during the summer? That's crazy!'
Now, the former 'Two and A Half Men' star admits his certificate is one of his proudest achievements.
"I am going to get a spotlight, cordon the thing off. I think it should be put up somewhere, maybe in the kitchen. This, I think, is important to put up," he said.
