Nassar was born on 5 March 1958 to Mehaboob Basha and Mumtaz Beghum as Mehaboob Nasser, in an interior village called Meylerippakkam, in Chengalpattu district, Tamilnadu. He studied in St. Joseph's Higher Secondary School (Chengalpattu). He moved to Chennai (then Madras) after school, where he finished his pre-degree at Madras Christian College. At Madras Christian College, he was an active member of the Dramatic Society. Later for a brief time, he was in the Indian Air Force.
Nassar is a Tamil actor, producer, writer, director, lyricist, and singer. He has appeared in Tamil, Telugu, Malayalam, Kannada, Hindi and English films. He is often cited as part of India's specialist character actors, along with the likes of Naseeruddin Shah, Om Puri and Nana Patekar. He is proficient in Urdu, English, Hindi, Arabic, Tamil, Telugu, Kannada and Malayalam. Nassar is married to Kameela and they have three sons.

With his experience as drama writer and actor, he started seeking chances to act in films, but he was not successful. Hunger forced him to suffer and at one point, he joined the catering department of Taj Coromandel Hotel, Chennai. While he was trying for chances in cinema, he also wrote stories and poems and sent them to newspapers and magazines. Some of them were published.
Nassar joined the Film Institute in Chennai, in the year 1982-83, and received his diploma in acting. Prior to this, he also underwent training in acting at the Acting Training Centre, affiliated to South Indian Film Chamber, Chennai. His efforts started bearing results when he was introduced as an actor in K. Balachander's film Kalyana Agathigal'.His full name then was Nasser Muhammad. He entered the film industry in 1985. He has acted in about 300 films, which include Tamil, Telugu, Malayalam, Kannada, Hindi and English language films. He also became popular in TV serials.
The telefilm Kaattuppookkal, directed by Mahendran, and the other one titled "Panagaadu", directed by Senathibathi elevated his popularity as an actor