A rep for the star tells us McCaffrey passed away Sunday surrounded by friends and family. We're told he'd been diagnosed with multiple myeloma, and that he ultimately succumbed to the disease.

His rep notes ... "One of Dick Wolf's proteges (""Swift Justice), McCaffrey went on to a successful 35 year career in television and film. Trained at the Actor's Studio, he never lost his love for creating characters; however, his good looks often pushed him toward leading man roles."

Word of McCaffrey's death first started to spread through a post from "Entourage" star Kevin Dillon -- who honored his friend with a photo of the both of them and a remembrance.

Like we mentioned, McCaffrey will perhaps best be remembered for serving as the voice actor for the 'Max Payne' video game series -- which included at least 3 installments -- but his resume went well beyond just that ... with TV and movie roles on big time shows.

The series he famously appeared in was "Rescue Me," where he portrayed Jimmy Keefe for 56 episodes between 2004 and 2011. Other shows he starred in included ... "Revenge," "Beautiful People," "Law & Order: SVU," "As the World Turns," "Swift Justice," "Civil Wars," "Canterbury's Law," "Suits," "Blue Bloods," "Bluff City Law," "She's Gotta Have It" and more.

Of course, he was also one of the leads for the famed "Viper" way back in the '90s. And McCaffrey acted in a number of major films as well -- "The Truth About Cats & Dogs," "The Big Take," "A Gifted Man," "American Splendor," "She Hate Me" ... just to name a few.

McCaffrey is survived by his wife Rochelle Bostrom ... and daughter Tiernan. He was 65.