The series regular was first introduced as a Russian officer during the Cold War, with the American actor putting on a heavy Russian accent for the role.
Star Trek ran on NBC from 1966 to 1969 – with its fans, Trekkies, keeping love for the franchise alive for decades longer.
Sharing his tribute online, George Takei, fellow actor and castmate, said: “My heart is heavy. Walter was more than Chekov. He was a writer, a teacher, a thoughtful man, and a loyal friend.”
He added: “Walter was more than Chekov. He was a writer, a teacher, a thoughtful man, and a loyal friend.