Karunakaran departs from Ambasamudram to Mumbai in order to seek a job so that he can earn money for his family and his sister's wedding. He lives with his elder sister and meets Nisha, who falls in love with him. Initially rejecting her, Karunakaran later accepts her love. Unable to find a job and through his old friend Chandru, Karunakaran joins as a henchman for a gangster named Supari, where he receives money for completing many assignments and is happy that he can help his family and sister financially. Unfortunately, Karunakaran's own gang members plan to kill Nisha after killing her parents. Karunakaran tries to protect her and earns Supari's wrath. What is Nisha's connection with the gang and how does Karunakaran save Nisha and his family from Supari's gang forms the crux of the plot.
Vijay recommended Isha Koppikar as the female lead to his father S. A. Chandrasekhar after being impressed with her performance in Kaadhal Kavithai, despite her lack of understanding of Tamil.[4][5] An item number was shot with actress Roja in late March 1999.[6] During the post-production stages, Chandrasekhar accused the son of K. Balachander of trying to make illegal copies of the film. The allegations prompted Vijay to pull out of a film he had agreed to act in under Balachander's production house.[7]
The film was released on 25 June 1999. D. S. Ramanujam of The Hindu appreciated Vijay's performance, Chandrasekhar's screenplay and the fight choreography, but said Chandrasekhar "leaves much to be desired" in the comedy subplot.[9] K. N. Vijiyan of New Straits Times wrote, "Those who go to see [Nenjinile] will either be fans of Vijay or those captivated by Isha".[10]Ananda Vikatan rated the film 35 out of 100.[11] However K. P. S. of Kalki gave a positive review, saying both Vijay and Chandrasekhar created a jugalbandi.[12] A critic from Sify wrote that "Somewhere along the line Chandrasekar loses his senses and the screenplay takes twists and turns which only confuse the viewer and many times defy logic. [...] Choreography and cinematography are good and Vijay scores in dances and fights".[3]