In a career spanning five decades, his repertoire extended to 25000 songs in various regional languages, including popular songs such as ‘Chalo ek baar phir se Ajnabi ban jayen hum dono’ Gumrah, ‘Neele gagan ke taale’ Hamraaz. His name however became most closely associated with patriotic songs including ‘Mere Desh Ki Dharti', in Manoj Kumar’s film Upkaar In 1972, he was awarded the Padma Shri by the Government of India.
Mahendra Kapoor was born in Amritsar, but soon moved to Mumbai. At an early age he was inspired by singer Mohammed Rafi but soon he started learning classical music under classical singers like Pt.Hussanlal, Pt. Jagannath Bua, Ustad Niaz Ahmed Khan, Ustad Abdul Rehman Khan and Pt.Tulsidaas Sharma. Kapoor created a style of his own and won the Metro Murphy All-India singing competition, which led to his debut as a playback singer in V. Shantaram’s Navrang in 1958, singing Aadha Hai Chandrama Raat Aadhi, under the musical direction of C. Ramchandra.
Kapoor had a very large vocal range, and he is sometimes known as The Vibrant Voice of India. He was the first Indian playback singer to record music in English. He was asked by the group Boney M to sing their songs in Hindi with Musarat from Pakistan, which resulted in the Pop Album M-3. Some of the songs on the album are "Chori Chori Chalo!!"(Original, Hoorray! Hoorray! by Boney M), "O' Meri Champe Ki Daali" etc.
Mahendra Kapoor also sang a duet with Mohammed Rafi. The song was "Kaisi Haseen Aaj Baharon Ki Raat" from the 1967 film "Aadmi", which was originally recorded as a duet with Rafi and Talat Mehmood. Manoj Kumar, one of the lead stars refused to use Talat's voice for him and the song was re-recorded with Kapoor replacing Talat. Mahendra Kapoor also sang the dohas,mantras,chopaiyan and also Title track of Mahabharat 1988 Tv series.
Kapoor sung in a large number of Indian languages, and is the playback singer who has performed in the largest number of in Gujarati, Punjabi and Marathi movies. He also performed the title song for the TV series Mahabharat. In Marathi he was very popular for being the voice of Dada Kondke in all his movies. In spite of being associated with Dada Kondke's colloquial style his singing for Marathi movies was not limited to Dada Kondke's movies only.
Kapoor was married and had three daughters and also one son. His son Rohan Kapoor is an actor and singer, who acted in a few films in the 1980s such as Yash Chopra's Faasle (1985) and Love 86 (1986), and Prakash Mehra's Imandaar, and later did stage shows together with his father.
On September 27, 2008, Kapoor died following a cardiac failure. He was survived by his wife, children, children-in-law and grandchildren.