Boogie Nights hunk Mark is executive producer of the HBO show, which follows a Hollywood actor and his entourage and is loosely based on his Hollywood lifestyle.
Older brother Donnie, who stars in horror sequel Saw II, believes the glossy entourage on the show are too clean-cut compared to real-life Tinseltown hangers-on.
Donnie says, "I personally don't like Entourage, because I know the real guys.
"To see those guys, it's like a Disney show. It really is toned down. These guys are nuts. They are."
Donnie is keen to clear up rumours the JOHNNY DRAMA character - the fading star and older brother of lead character VINCE CHASE - is based on himself.
He explains, "There is a real Johnny Drama and it's not me.
"I wouldn't feel bad about it because the guy loosely based on Mark is so horrible. It's nothing like Mark."