He was born to Vadivelu and Muthulakshmi in Tamil Nadu, India. He joined the Auditor Generals Office as a Junior Division Clerk in 1976 and worked part-time as a Theatre artist and a stage artist due to his desire to act and perform. He was friendly with Delhi Ganesh, another AGS employee who remains his closest friend to date.
He found his break in 1980 in Nizhalgal after several insignificant roles and by the middle 1980s was among the most wanted comedians, having roles with major movie stars like Sivakumar, Rajinikanth, Kamal Hassan, Rahman and with major movie directors like Mani Ratnam, K. Balachander and Suresh Krishna.
In 1971, Janagaraj began to aspire for a movie career. Director K. Balachander offered him a chance to perform in very minor roles in several Tamil films from 1972 until 1977. It was in 1977 that he landed his first speaking role in Sevuppu Villu, a Tamil film starring actor Ravichandran. He continued minor roles through the late 1970s.
Janagaraj's career however spun silver in the 1980s. Starting with Nizhalgal (1980), Paarvai (1982), and continuing in Apoorva Pirargal (1983), Sindhu Bhairavi (1985), Palaivana Rojakkal, Muthal Vasantham (1986), Rajadhi Raja (1989), Apoorva Sagodharargal (1989), and Agni Natchathiram (1989), Janagaraj became a popular comedian in Tamil. He is known for his peculiar voice and face expression. Janagaraj has also acted in supporting roles in films like Nayakan, Annamalai (1992) and Baashha (1995). He was main sidekick for Kamal Haasan and Rajinikanth in 80s and early 90s movies.
Janagaraj has also acted in character roles in films like Nayagan (1987), Kizhakku Vasal (1990) Annamalai (1992) and Baashha (1995). His latest roles were in King (2002), Aayutha Ezhuthu (2004), and M. Kumaran S/O Mahalakshmi (2004) in supporting roles.