After Ashok Kumar became a star of Hindi films, the Ganguly family visited Bombay (now Mumbai) regularly. Abhas Kumar changed his name to ‘Kishore Kumar’ and started his cinema career as a chorus singer at Bombay Talkies, where his brother worked. Kumar’s first film appearance was in Shikari (1946), in which his brother, Ashok played the lead role. Music director Khemchand Prakash gave Kumar a chance to sing “Marne Ki Duayen Kyon Mangu” for the film Ziddi (1948). After this, Kumar was offered many other assignments, but he was not very serious about a film career. In 1949, he settled in Bombay. Kumar played the lead in the Bombay Talkies film Andolan (1951), directed by Phani Majumdar. Although he got some acting assignments with the help of his brother, he was more interested in becoming a singer. But Ashok wanted Kumar to be an actor like him. Between 1946 and 1955, Kumar appeared in 22 films of which 16 were flops and since he was disinterested in taking up acting as a career, he would find ways to be in the bad books of the director or producer, so that they throw him from their films. It was only after the success of films such as Ladki, Naukari, Miss Malaysia, Char Paise and Baap Re Baap that Kumar developed an interest in acting seriously, which resulted in him having successful films as the lead actor between 1955 and 1966.

Kumar married four times. His first wife was Bengali singer and actress Ruma Guha Thakurta aka Ruma Ghosh. Their marriage lasted from 1950 to 1958. His second wife was actress Madhubala, who had worked with him in many films including his home production Chalti Ka Naam Gaadi (1958) and Jhumroo (1961). When Kumar proposed to her, Madhubala was ill and was planning to go to London for treatment. She had a ventricular septal defect (hole in the heart), and he was still married to Ruma. After his divorce, the couple had a civil wedding in 1960 and Kumar converted to Islam and reportedly changed his name to Karim Abdul. His parents refused to attend the ceremony. The couple also had a Hindu ceremony to please Kumar’s parents, but Madhubala was never truly accepted as his wife. Within a month of their wedding, she moved back to her bungalow in Bandra because of tension in the Kumar household. They remained married, but under great strain for the remainder of Madhubala’s life. Their marriage ended with Madhubala’s death on 23 February 1969.

After 1966, as an actor, Kumar built up a notoriety for coming late for the shootings or bunking them altogether. His films flopped frequently after 1965 and he landed in income tax trouble.

In 1968, Rahul Dev Burman worked with Kumar on the soundtrack of the film Padosan (1968), in which Kumar sang “Mere Saamne Wali Khidki Mein” and “Kehna Hai.” Padosan was a comedy featuring Kishore as a dramatist-musician, Mehmood as a Carnatic music and dance teacher, and Sunil Dutt as a simpleton named Bhola. Kishore’s character was inspired by his uncle, Dhananjay Bannerjee, a classical singer. The highlight of the film was a musical, comical duel between Kumar, Sunil Dutt and Mehmood: “Ek Chatur Nar Karke Singaar.”

In 1969, Shakti Samanta produced and directed Aradhana. Kumar sang three songs in the film; “Mere Sapnon Ki Rani”, “Kora Kagaj Tha Ye Man Mera” and “Roop Tera Mastana”. Shakti Samanta suggested that Kumar sing the other songs too. When the film was released, Kumar’s three songs established him as a leading Bollywood playback singer. Kumar won his first Filmfare award for “Roop Tera Mastana”.

Kumar produced and directed some movies in the late 1970s and early 1980s; Pyar Zindagi Hai, Badhti Ka Naam Dadhi (1978), Sabaash Daddy, Zindagi (1981), Door Wadiyon Mein Kahin (1980) and Chalti Ka Naam Zindagi (1982)—which was his last appearance as an actor. Kumar’s son Amit Kumar became a Bollywood singer in the 1974 with the song “Apne Bas Ki Baat Nahi”, composed by Kumar for the film Badthi Ka Naam Daadi. Amit Kumar became popular with success of the song “Bade Achche Lagte Hai”. Kishore continued singing for several actors even in 1980s. Kumar performed stage shows right from 1969 to earn money to pay his income tax arrears. Kumar stopped singing for Amitabh Bachchan in the year 1981, after Bachchan refused to appear as a guest in the film Mamta Ki Chhaon Mein, which Kishore produced. Kishore declined to give voice for Amitabh in Naseeb, Coolie, Mard and Desh Premee. Kishore said he would give his voice to Randhir Kapoor in the film Pukar. Since Kishore shared good rapport with R. D. Burman, he agreed to sing in Mahaan, Shakti and Bemisal. Later, Kishore called a truce by singing for Amitabh in a solo song in Shahenshah and later in Toofan. Kishore sang the song “Mera Geet Adhura Hai” for his production Mamta Ki Chaon Mein and picturised the song on Rajesh Khanna. Kishore had directed the film, but died in 1987 and Rajesh Khanna helped Amit Kumar in releasing the film in 1989. He also temporarily stopped singing for Mithun Chakraborty after Yogeeta Bali divorced him and married Chakraborty. However, he later sang for Chakraborty in Surakshaa in the 1970s, and in the 1980s in many films, including Boxer, Jaagir, Fareib and Waqt Ki Awaz.

S. D. Burman and Kishore continued with music including “Phoolon Ke Rang Se” and “Shokhiyon Mein Ghola Jaaye” from Prem Pujari (1969), “Pal Bhar Ke Liye” from Johny Mera Naam, “Aaj Madhosh Hua Jaye Re,” “Khilte Hain Gul Yahan” and “O Meri Sharmilee” from Sharmilee (1971), “Meet Na Mila” from Abhimaan (1973), and “Jeevan Ki Bagiya Mehkegi” from Tere Mere Sapne (1971). In 1975, S. D. Burman composed his last song for Kishore, “Badi Sooni Sooni Hai” for the film Mili.

Kishore also worked with other composers including Rajesh Roshan, Sapan Chakraborty and Bappi Lahiri. Kumar sang “Bhool Gaya Sab Kuchh” (duet with Lata Mangeshkar) and “Dil Kya Kare Jab Kisise” for Rajesh Roshan’s film Julie. Their other songs include “Yaadon Mein Woh” from Swami, “Chhookar Mere Man Ko Kiya Toone Kya Ishaara” from Yaarana, “Kaha Tak Ye Manko Andher Chalenge” from Baton Baton Mein, “O Yara Tu Yaro Se Hai Pyar”, and “Laharon Ki Tatah Yaadien” (1983) and Kahiye, Suniye (duet with Asha Bhosle) from Baton Baton Mein. Bappi Lahiri also recorded many songs with Kumar, including Pag Ghunghroo Bandh from Namak Halaal (1982), Manzilen Apni Jagah Hai from Sharaabi (1984), “Chalate Chalte Mere Ye Geet Yad Rakhana” from Chalte Chalte (1975) and “Saason Se Nahi Kadmose Nahi” from Mohabbat (1987) and duets with Lata Mangeshkar such as “Albela Mausam” and “Pyar Ka Tohfa” from Tohfa (1984). The Kishore and Bappi pair also recorded hits in Bengali, including “Chirodini Tumi Je Amar” from Amar Sangi (1987) and “E Amar Gurudakshina” from Gurudakshina (1987). Another Bengali musician was Ajay Das, who composed many hit songs in Kumar’s voice. He also recorded a duet song Hello Hello Kya Haal Hai with Asha Bhosle for Naushad in 1975 for the movie Sunehra Sansar, the only song of Kishore. He also worked with music directors Basu and Manohari Singh for duets such as “Wada Karo Jaanam” and “Dariya Kinare” for the film Sabse Bada Rupaiya and “Aa Humsafar” for the film Chatpatee.

He had recorded the duets “Kaho Kahan Chale” for the film Bulundi, “Pyar Ka Dard Hai” from Dard and “Tum Jo Chale Gaye” from Aas Paas, a few days before his heart attack in 1981. He suffered his first heart attack on 24 January 1981 in Kolkata in the noon hours and within a gap of another four hours, suffered his second heart attack. The first solo song sung by him, after recovery from his two attacks was “Mere Sang Sang Aya” from Rajput (1982) and the duet with Asha – “Mausam Bheega Bheega” from Gehra Zakhm.

In the mid-1980s, Kishore sang for Anil Kapoor in Kapoor’s debut film as a leading man, Woh Saat Din and also recorded for Mr. India. (1987) the song “Zindagi Ki Yahi Reet Hai Haar Ke Baad Hi Jeet Hai”. He sang duets with Alka Yagnik such as “Tumse Badhkar Duniya Mein Na Dekha” for Kaamchor in 1982, “Humnashi Aaake from Ek Daku Saher Mein” and sang “Teri Meri Prem Kahani” in Pighalta Aasman.

Kumar was a loner; in a 1985 interview with Pritish Nandy he said that he had no friends—he preferred talking to his trees instead. Once, when a reporter made a comment about how lonely he must be, Kumar took her to his garden, named some of the trees there and introduced them to the reporter as his closest friends.

By September 1987, Kumar had decided to retire as he was unhappy with kind of songs and tunes being made by music directors and was planning to return to his birthplace Khandwa.

In 1996, nine years after his death, Kumar’s vocals from the song Saala Main Toh Saab Ban Gaya were used in the movie, Raja Hindustani and picturised on Aamir Khan. Kumar originally sung it for Dilip Kumar and it is from the film, Sagina.

Kumar’s unreleased song was sold for Rs 15.6 lakh at the Osian’s Cinefan Auction, New Delhi in 2012, the highest price bid for any Indian singer. The song was “Tum hi to woh ho”, written by Kulwant Jani with music by Usha Khanna. This was for a film called “Khel Tamasha” by Rakesh Kumar, which never got made. The song was recorded just three days before his death in October 1987.