True Blood's creator Alan Ball told The Hollywood Reporter: "Nelsan was a singular talent whose creativity never ceased to amaze me. Working with him was a privilege."
Ellis' True Blood co-stars Joe Manganiello and Sam Trammell took to Twitter to remember the actor.
"Crushed today by the loss of my friend and castmate Nelsan Ellis," Manganiello wrote. "He was a wonderful person, a pioneer, and a one of a kind artist. RIP."
"I don't know if I've ever seen the level of humility and kindness that came with the magnificent talent that Nelsan Ellis had. Miss u friend," added Trammell.
Empire star Gabby Sidibe tweeted her shock, saying: "Heartbroken over the passing of Nelsan Ellis. He was always so sweet to me and so entertaining to watch in screen."
Although most known for his work on True Blood, Ellis had major roles in films such as The Help, The Soloist, The Butler, Secretariat, and Get on Up, the biopic of James Brown.