Harvinder (Govinda) is a 40-year-old man living in London with his parents Laxminarayan Srivastav (Anupam Kher) and Maya Srivastav (Smita Jaykar), an ardent lover of the lord. He's still a virgin and sleepwalks in the nights. One night he sleepwalks into an unknown white woman's bedroom causing mayhem for her lover until the white woman's husband shows up. Sanjeev's father seeks the help of his employee Shafarat Ali (Shakti Kapoor) and his nephews to help Sanjeev lose his virginity, but all their efforts are futile. This brings embarrassment to LM Kapoor.

Happy's friends attempt to hook him up where one of his friends talks to a Chinese girl who then leads Happy to her room. However, much to the dismay of Happy, he discovers "she" is a man. The next day, Randy, Sandy and Shafarat Ali leads Happy to the massage parlour. Happy then accidentally breaks the female massage parlour's nose. In a fit of fear, they break into a run. LM Kapoor then invites Happy to Uncle Chatur's (Sanjay Mishra) house, who is a heart patient, where Happy is head over heals over his daughter however one night, Happy ends causing trouble for another woman due to sleeping on her bed. Because of his sleep-walking problem, girls reject him.

The family leaves for Manali, where Sanjeev gets married to Gauri (Yuvika Chaudhary), a girl much younger than him. However, Gauri is up to childish pranks all the while, which results in Sanjeev getting into a physical relationship with a London based model who is in the town for photo shoot. Sanjeev thinks nobody will find out, but when Gauri does discover the truth, she gets a rude shock, which brings about a change in her attitude.

• Govinda as Harvinder Srivastav (Happy Brother)
• Yuvika Chaudhary as Gauri
• Anupam Kher as Laxminarayan 'Allan' Srivastav (LM Kapoor)
• Shakti Kapoor as Sharafat Ali
• Smita Jaykar as Maya L. Srivastav
• Harish Kumar as Sandeep / Sandy (Sanjeev's cousin)
• Sanjai Mishra as Sanjeev's uncle
• Sayali Bhagat as Woman who rejects Sanjeev
• Rakesh Bedi as Dayashankar (Gauri's father)
• Gurpreet Ghuggi as Laxminarayan's employee
• Satwant Kaur as Sayali's Mother

The album consisted of 4 tracks and was released on Venus music label.

The movie's release was delayed for more than 2 years when the producers Anuj Sharma and Sandeep Kapoor had a fall out. Kapoor approached the Delhi High Court in 2009 seeking recovery of a loan of ? 1.32 crore which he had allegedly advanced to Sharma. Justice V.K. Jain allowed Sharma to go ahead with the film's release after his lawyer deposited a demand draft of ? 1 crore with the court registry. However, the court declined Kapoor's plea to release the amount to him stating "The question of release of money to the petitioner (Kapoor) would be decided after the entire amount is deposited with the court". He also asked Sharma to pay the remaining amount by 6 April 2011.

Naughty @ 40 opened to mixed reviews from critics. Taran Adarsh of Bollywood Hungama rated the film with two stars out of five saying, "The film is for the hardcore masses who relish double entendres and saucy jokes." Rajeev Masand of CNN-IBN gave the film three stars out of 5 and stated, "Naughty @ 40 is a non-stop laughathon." Anupama Chopra of NDTV gave two and a half stars and commented, "Looked really good with all the trailers, but turned out as one of those rare films that barely get anything right!" Nikhat Kazmi of the Times of India awarded two and a half stars saying, "You have a film that can be an average weekend getaway. Nothing more, not even the plot of the laugh riot The 40-Year-old Virgin."