Ranjith was born into a Malayali family, hailing from Kalluvazhi, Kerala. He grew up listening to various kinds of music. He learned Hindustani music and Carnatic music. He was trained by Vidwan Cuddalore Subramanian, K. S. Kanakasingam, Trichur P. Ramankutty and P. S. Narayana Swamy. He is married to a trained Bharata Naatiyam dancer, Reshmi Menon. He has a daughter named Ria. Mani Sharma introduced Ranjith as a playback singer, calling him to sing the song "Adugu Adugu" for the Telugu film Bobby. Ranjith's first Tamil song was "Hey Penne" from Aasai Aasaiyai, also composed by Mani Sharma. However, the song which gained Ranjith popularity was "Suppose" from the film Sukran (2005). In 2007, he sang his first song in his mother tongue Malayalam, "Innoru Paattonnu Paadaan" for the film Kilukkam Kilukilukkam. In 2005, Ranjith composed, arranged and performed an ensemble of Ayyappa Namaskara Slokas that was complied into an album titled Saranam Ayyappa. He further composed and arranged the music for the dance ensemble Panchamukhi. He has worked often with Yuvan Shankar Raja, Vidyasagar and other music directors in Tamil.