Like his father, he is also a singer, composer, actor, filmmaker but also a music company owner. Like his father, he is also wedded to music. He eats music, drinks music, and breathe music. Like his father, Amit started singing from an early age and he used to sing at Durga Pooja festivals in Calcutta.
When he was 11, his father brought him as his son in the films that he produced, Door Gagan Ki Chhaon Mein' in 1961. When he was a teenager he sang for the film ' Door Ka Rahi.but it was removed from the final cut of the film.
He sang professionally for the first time, outside his father's composition, at the age of 21 in 1973. The song was "Hosh Mein Hum Kahan", composed by Sapan Jagmohan for the film Darwaza, which was released in 1978. Officially his first released song was in Main Bhi Akela Hoon from the 1974 film Zindagi Aur Toofan.
He came into the limelight after the song "Bade Achchhe Lagte Hain" composed by R.D. Burman, for the film 'Balika Badhu' in 1976, the song was a hit. After this song he was one of the favorites of R D Burman. He sang 170 songs under him.
His duets with his father, such as "Haseeno Ke Chakkar Mein" from Deewangee in 1976, "Nazar Lage Na Saathiyo" from Des Pardes in 1978 and "Sun Chache Bol" from Badthi Ka Naam Dadhi in 1974 became popular. His duet with Asha Bhonsle and Lata Mangeshkar also became popular, by 1980 his songs were becoming hit. In 1981 after the release of Love Story, he was the most sought after singer after Kishore Kumar. In this film, he sang all the songs for Kumar Gaurav and became his screen voice.
After the success of Love Story, Rajesh Khanna employed Kumar for playback singing in Fiffty Fiffty (1981) and then later in Aakhir Kyon? (1985), Ghar Ka Chirag, Jai Shiv Shankar, Swarg (1990) and Sautela Bhai (1996).
Among music directors, Amit Kumar was used more by Pancham from 1975 to 1994 and by Bappi Lahiri from 1983 to 1995. He sang for almost all music directors and actors of that time. He sang songs for Anil Kapoor in films including Tezaab, Yudh, and Aag Se Khelenge and continued to sing for him in the 1990s.
After the death of R.D. Burman in 1994, with whom Amit had a special bond, he withdrew himself from the film industry. Kumar started undertaking more live stage performances in various parts of the world since 1996.
Amit Kumar also acted in several films directed by and starring his father, which were Door Gagan Ki Chhaon Mein (1964), Door Ka Raahi (1971), Badhti Ka Naam Dadhi (1974), Shabhash Daddy (1979) and Chalti Ka Naam Zindagi (1982). In 1989, he made his last film appearance in his father's incomplete film Mamta Ki Chhaon Mein, which starred himself, his stepmother Leena Chandavarkar and Rajesh Khanna. After his father's death in 1987, he took over as director and completed the film for release in 1989. In his long career in the film, he acted in a Bengali film namely "Gayak". In this film the name of his character was Amit and it was of a struggling singer. He sang a number of songs for this film under the direction of Rabin Banerjee.
Nowadays he is away from Bollywood, Amit does not even follow what is happening in the Hindi film industry on the music front.