Jogan in 1950 in which he starred opposite Dilip Kumar and Nargis. He was then noticed in Mother India in 1957 in which he played Nargis's son which was a huge hit.
After that he had many successful box office hits including Dhool Ka Phool (1959), Mere Mehboob (1963), Sangam (1964), Arzoo (1965) and Suraj (1966). He was considered a golden boy for the movie producers in the sense that he was the actor who could recover the producers' money in a matter of few weeks. He was nicknamed "Jubilee Kumar" because most of his films in the 1960s particularly completed Golden or Silver jubilees at the box office.
However, the mid-1970s proved devastating for Rajendra Kumar. Several of his films bombed at the box office, and he was not getting the offers he used to receive earlier. It was the bleakest point in his career as he said in an interview. However, the sunshine came when he was offered an interesting role in the film Saajan Bina Suhaagan opposite Nutan. The film was a huge blockbuster of 1978. Rajendra Kumar had regained his 'Midas Touch'.
In 1981 Rajendra Kumar stepped aside, and made way to welcome his son Kumar Gaurav in the film Love Story which he produced and also starred in. The film was declared the blockbuster of 1981. But the success was shortlived as Kumar Gaurav's later films were huge disappointments at the box office and his son's career declined as soon as it began. Rajendra also produced and acted with his son in Phool in 1993 but this was also a failure. Kumar's last film appearance was in Deepa Mehta's Earth in 1998.
He was also a co-producer of the 1994 adaptation of Rudyard Kipling's book The Jungle Book.
He died in July 1999 of cancer only nine days after his 70th birthday. He was known to never have taken medicines in his entire life.