Unni Menon was born to V. K. S. Menon, an officer in Tamil Nadu police and a native of Valanchery in Malappuram district and Malathy. He did his schooling in Guruvayoor and B.E.M. High School, Palakkad. Later, he attended the Government Victoria College, Palakkad, from where he graduated with a degree in Physics. He is basically a Malayalam film playback singer. Kunjunni, a violinist for music director Ilaiyaraaja introduced him to B. A. Chidambaranath, a music director, and Unni's musical career was launched in 1981–82. He was a track singer and after listening to his tracks for the film, Kadathu, KJ Yesudas asked to the music director, Shyam, to make it straight. And after the huge success of the Kadathu songs, Unni became a regular singer for the hit music director, Shyam. Shyam has given him a good number of popular songs like "Maanathe Hoori Pole" (Ee Naadu), "Valakilukkam Oru Valakilukkam" (Munnettam), "Kaayampoo Korthu Tharum" (Aarorumariyaathe) and "Thozhuthu Madangum Sandhyayumetho" (Aksharangal). He has also given some hit private albums such as Raagageethi and Raaga Lahari, with his contemporary playback singer, Ashalatha. Soon he had graduated from singing tracks for prominent singers and was becoming a singer sought after by many music directors. In 1980s he had few lone hits in Tamil film 'Oru kaidhiyin dairy', singing for Ilayaraja. His career got a major boost in 1992 when A. R. Rahman offered him the song "Puthu Vellai Mazhai". That song went on to become a huge hit, as were all the other songs from the film. Since then he has sung many songs which have become big hits. He is the leading Singer in 2009 Malayalam Devotional Album Saranamanthram directed by Kamalan. He has frequently associated with A. R. Rahman, lending his voice to nearly 25 memorable songs from films like Karuththamma (1994) and Minsaara Kanavu (1997).