Walker was the son of late Hollywood stars, actor Robert Walker and Oscar-winning actress Jennifer Jones. He was 79 years old.
StarTrek.com reported the sad news on Friday, citing his family. Star Trek's official Twitter account also tweeted about his death.
"We are saddened to report the passing of Robert Walker Jr., the actor who played the titular role in Star Trek: The Original Series episode 'Charlie X.' #StarTrek #StarTrekFamily," the tweet reads.
According to The Hollywood Reporter, Walker died on Thursday in Malibu, California. The cause of death is unknown.
Walker is most known for his role in the Star Trek series, appearing in the second episode as Charlie X, the sole survivor of a shuttle crash. It is later discovered in the 1966 episode after he is rescued that he has special powers.
Aside from his role in the classic Star Trek episode, Walker's other memorable roles included parts in popular television shows such as Bonanza, Charlie’s Angels, Colombo, and Murder, She Wrote. His film roles include the 1969 films Easy Rider and Young Billy Young.
He is survived by his wife, Dawn, and his seven children -- Michelle, David, Charlie, Jordan, Colette, Henry and Emily -- as well as five grandchildren.