Featuring Rajinikanth in a dual role, it revolves around the eponymous con artist who is implicated for a crime committed by Vidyasagar, a lookalike barber.

Though Johnny is upset on never getting recognised legally as a son, he decides to help his father by clearing his loans.

Once when he returns home after getting drunk and losing control, he is helped by Bhama, a homeless orphan.

To protect Vidyasagar from the police, Johnny tells him to remain home for 10 days so that he can resolve all issues and come clean.

When Archana misunderstands his hesitation, thinking he is doubting her integrity and character, Johnny confesses his love and seeks time to settle a few things before marrying her.

When Archana explains that she compensated Johnny's victims at the cost of her wealth, Vidyasagar is disappointed.

Though Vidyasagar had come with plans to win her and grab her wealth, her character and love for Johnny stop him, and he reveals his true identity.

He first drew the illustrations of scenes with costumes and then got them stitched, bringing in newness and style in Rajinikanth's look, which attracted the masses.

[3] The scene where Archana (Sridevi) proposes to Johnny was shot in Ooty in a bungalow at midnight.

[5] Kavitha Muralidharan of The Hindu wrote that most of Mahendran's films, including Johnny, "offer a prismatic view of relationships".

[6] Mani Prabhu of Cinema Express described Johnny as an antithesis to the "lead man of those times – the macho guy, surrounded by drooling girls, bashing up villains and spouting pretentious advice" by being "vulnerable, loving and grounded".

[8] The song "Oru Iniya Manathu" is erroneously credited to Jency on the original LP record marketed by Inreco,[9] but actually sung by Sujatha.

However, the emotionally moving story, intense acting by Rajinikanth and Sridevi and songs attracted the audience, so the film picked up in the third week and became a success,[21] running for over 100 days in theatres.

[22] Piousji of the magazine Sunday wrote, "Sridevi not only looked smart, but came out with a convincing performance and [Rajinikanth] too was quite impressive" in Johnny.

[22] Writing for Kalki, Nalini Sastry appreciated the film for eschewing Tamil cinema conventions such as fight scenes, club dances and loose fitting clothes, noting that Mahendran's direction, Ilaiyaraaja's music and Ashok Kumar's cinematography gave them the feeling of watching an American film.

[24] Naagai Dharuman of Anna lauded Rajinikanth's dual role performance, Ashok Kumar's cinematography and Ilaiyaraaja's music.