Mahendra Kapoor was born in the holy city of Amritsar on the 9th of January 1934. He belonged to a family of cloth dealers. While Mahendra was still young, his family migrated to Bombay. Since childhood, he showed a keen interest in music. BM Vyas, a character artist in Prithvi Theaters became his first guru. He attended St. Xavier school in Bombay . During his school days, he gave audition of Young India Company and also for All India Radio but didn’t get selected. He did not give up, and continued his practice under Ustaad Meherji, Ustaad Niyaz Ahmad Khan, Pt. Tulsidas Sharma and Manohar Potdar.

Though he started his career somewhere around 1953, music director Snehal Bhatkar gave him his first major break in the film 'Diwali Ki Raat' (1956). Mahendra sang a solo 'Tere dar ki bheekh maangi hai data' which was penned by Madhukar Rajasthani. In the same year, Mahendra recorded a duet for music director Sanmukh Babu in the film 'Lalkar’ called 'O bedardi Jaane ken a kar bahane', with co-singer Savita.

In 1957, Metro Murphy singing contest was organized, wherein the judges constituted the topmost music directors of the Hindi film industry, viz. Anil Biswas, C Ramchandra, Madan Mohan, Vasant Desai and Naushad. Mahendra won the contest and found himself receiving a lot of appreciation and the much needed exposure.

Naushad then recorded the climax song of 'Sohni Mahiwal' in the year 1958, 'Chhupa aur tare doobe, raat milan ki aayi', with Mahendra Kapoor which was a run-away hit. Shaqeel Badayuni's lyrics and Mahendra’s singing appealed to the masses, and impressed music director C. Ramchandra, who recorded four songs with him for V. Shantaram's 'Navrang’ the following year. The songs were, 'Ja re hat natkhat' (with Asha), 'Na raja rahega na rani rahegi' (with Asha), 'Shyamal shyamal baran' and 'Aadha hai chandrma raat aadhi' (with Asha). These songs did more than just establish him in the industry; they made Mahendra Kapoor a household name and proved to be some of the biggest hits of the year.

Noted director B R Chopra offered him songs in 'Dhool Ka Phool' (1959), under MD N Datta. 'Tere pyar ka aasra chahta hoon' (with Lata) became a superhit, and is remembered till date as one of his best songs. BR Chopra offered him songs in his next projects, 'Dharamputra’ (1961) under N Datta and 'Gumrah’ (1963) under MD Ravi. Songs from the latter are arguably Mahendra’s best work, and his biggest hits. 'Chalo ek baar phir se’ even won him his first Filmfare award for Best Playback Singer in 1964

Hailed as one of the most popular singers of his time, he has sung with almost every singer across generations, like Mohd. Rafi (who he considers his idol), Mukesh, Talat Mahmood, Manna Dey, Kishore Kumar, Lata Mangeshkar, Asha Bhosle, Geeta Dutt, Shamshad Begum and Suman Kalyanpur. He has sung quite a few songs with Geeta, some of which became big hits.

They first sang together when Mahendra Kapoor was just starting his career in 1955 for the movie 'Madhur Milan' along with Rafi and A.R. Ojha. Mahendra had only a few lines to sing and his name didn't appear on the record (though it is mentioned in the Geet Kosh). Music director for the movie was the legendary Bulo C Rani.

Their first hit came in the year 1959 under Suresh Talwar's baton for the movie 'Fashionable Wife'. 'Jhoomo Re Jhoomne Ke Din Aaye' was a frolicky number where the light emotion of the song was conveyed beautifully by the two voices.

The following year, they appeared in a group song (with Lata, Manna and Mukesh) for Shankar-Jaikishan for the movie 'Jis Desh Mein Ganga Behti Hai', 'Hai Aag Hamaare seene mein' where all the singers brought forward the sentiments of the protagonists in this 1960 Raj Kapoor classic. Both Geeta and Mahendra got only two lines to sing, but their voices blended beautifully with the other three voices in the song.

Music director duo Kalyanji-Anandji used their voices in 'Dil Bhi Tera Hum Bhi Tere' in the song 'Aadmi gharib ho, sambhalo dil zara' in the same year, yet another fun song, sung by the two very well.

In the meantime, maestro S N Tripathi also utilised their voices in his Bhojpuri venture 'Jogin' in two songs, 'Sagre bahnwa se samujhe na manwa ho' and 'Ladkaiyan ma wa jab ee chohna to jawaani ma ka' to which both artistes did full justice.

The same year, Bulo C Rani used them in his movie 'Black Tiger' in the song 'Parwana Kehta Kya Afsana' during the time when he was struggling to get back into the limelight. The song although very melodious, did not really appeal to its audience and could not bring him back into reckoning. The two also appeared together in another obscure movie 'Lady of the Lake' in the same year in the song 'Sun re O chhaliya bole kya paayaliya'.

They next sang the song 'Gham ki aag mein hum to jalte yahan' for S.N. Tripathi in the 1963 movie 'Pareeksha'. This was the typical sad song which was the métier of both singers, and came out exceptionally well, besides being one of the biggest hits of that year.

In 1964 they sang just one song together, 'O Mister Johnny mizaaj kaisa hai' in yet another lesser known movie 'Tarzan & Captain Kishore'. By then Geeta's career was not in the best of shapes after her husband, Guru Dutt's demise. After this, they appeared together in only one song 'Rukh pe paaudar lab pe surkhi' from the movie 'Hum Kahaan Ja Rahe Hain?' under Basant Prakash's baton. Ironic, isn't it that the two singers never got together again?

By that time, Mahendra Kapoor had become one of the most sought after singers in tinsel town while Geeta was not singing much. His favourite music composer, Ravi had always had Asha Bhosle as his main singer. By the time O P Nayyar started using Mahendra Kapoor frequently as his singer; Geeta Dutt was long out of his recording room.