Sonu started his career singing covers of Mohammad Rafi songs. His first movie as a playback singer was (Janum). Again he got his big break as a playback singer in Gulshan Kumar's film (Aaja Meri Jaan) and then "Accha Sila Diya Tune" (also sung in Gujarati) from Bewafa Sanam (1996). At this time, he also started hosting Sa Re Ga Ma, a television singing talent competition that became one of the most popular shows on Indian television. Thereafter, the offers poured in, albeit slowly at first. He shot to fame with the song "Sandese Aate Hai" from Border (1997). In the initial stages, he was type-cast as a Rafi-sound-alike. The image was transformed after his brilliant rendition of "Yeh Dil, Deewana" in the film Pardes (1997). Since then, he has created a unique trademark style of his own.

Over the years, Sonu Nigam has become a major force in the music industry. He has released a number of pop albums including Mausam, Sapnay Ki Baat, Kismat, Deewana, Jaan, Yaad, Chanda Ki Doli and Colours of Love, as well as a Punjabi album 'Pyar'. Besides SaReGaMa, he has also hosted Kisme Kitna Hai Dum and been a judge on Indian Idol.

Sonu has sung playback for countless Hindi movies. As well, he is a popular playback singer for many regional movies, singing effortlessly in many languages from Kannada, Punjabi to Bengali to Telugu, and many more. He is very famous in South Indian movies especially in Kannada.