The actor, who has played Entourage's Hollywood superstar Vincent Chase for eight seasons, explained that it was difficult for him and his co-stars to maintain composure during the final shooting day.
"It was totally bittersweet," Grenier told Access Hollywood. "It was like the last day of high school - grown men were being reprimanded and we couldn't focus."
Grenier further explained that he would have enjoyed continuing Entourage beyond its eighth run, and added that a movie adaptation will "absolutely" be produced.
"The thing about Entourage is that it's [about] the ups and downs of the business and life that always flow," he said. "I think there is more time and opportunity to explore that."
Fellow Entourage star Jeremy Piven has also claimed that the series finale leaves open the possibility for a feature film continuation.
The final season of Entourage premieres on July 24 on HBO.
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Watch a preview of Entourage's final season below: