The Anger Management star will introduce a segment honouring party movies, according to E! Online.
"Even though Charlie has cleaned up his act, he still has a sense of humour about his out-of-control days," a source told the website.
A second insider said: "It's all going to be a really big party moment."
Pattinson, a regular at previous MTV Movie Awards shows, will reportedly skip the ceremony in spite of the fact that his girlfriend Kristen Stewart will be attending.
The MTV Movie Awards will be hosted by Russell Brand. Stewart, Emma Stone, Andrew Garfield, and Michael Fassbender are among the presenters.
The Hunger Games and Bridesmaids are tied for the most nominations, with eight nods apiece.
The 2012 MTV Movie Awards will air on Sunday, June 3 at 8/7c on MTV from the Gibson Amphitheatre in Universal City, CA.