Mahendran later revealed that Kamal Haasan helped him financially when he couldn't convince the producer of Mullum Malarum to allocate additional funds to shoot certain critical scenes. Mahendran and Kamal Haasan never got to work together but shared a great deal of respect and friendship.
Balu Mahendra (himself a legendary filmmaker who made films like Moondram Pirai/Sadma, Kokila and Veedu) served as the cinematographer for this film. Through this film Mahendran and Balu Mahendra brought a cinematic visual coherence to Tamil cinema which up until that point had a stage-play type look. Balu Mahendra predominantly used natural light to shoot the film.
The screenplay is adapted from a 1966 serial novel 'Mullum Malarum' by Uma Chandran. The novel was published in the magazine 'Kalki' and won the best novel competition conducted by the magazine. Mahendran made a bunch of changes to the story while adapting it to the screen.
When Mahendran was struggling to find a cinematographer Kamal Haasan introduced him to Balu Mahendra with whom Kamal had previously worked in Kokila (1977). Kamal Haasan also served as an uncredited production manager in the film.
At the time when Indian cinema was obsessed with fair skinned protagonists, Rajinikanth broke the stereotype and became the first dark skinned superstar. Mullum Malarum was instrumental in his rise as a protagonist who until then was mostly cast as the stereotypical "dark skinned antagonist". Rajinikanth changed the way film heroes were supposed to "look".