An Indian Muslim high school girl Insia (Zaira Wasim) and her mother Najma (Meher Vij), live with her younger brother Guddu and an overbearing father Farookh (Raj Arjun). Insia is very passionate about singing, but her father is completely against her dream of becoming a singer.
One day, Farookh goes out of town for work, and returns only once a week. Insia wants to participate in a music contest, which has a laptop and one free year of internet as a prize. Her mother tells her to get the permission of her father, but Insia never gets the chance as her father is busy scolding her and her mother. To satisfy her, Najma gifts Insia a laptop. Delighted with her present, Insia spends all her time on the laptop. She soon discovers that people have been using YouTube as a platform to record and post their songs. Insia records a song, while disguising herself anonymously in a niqab so that her father does not find out, and uploads the video on YouTube under the name of 'Secret Superstar'. She becomes an overnight sensation and grabs the attention of Shakti Kumar (Aamir Khan), who is a talented but rude music director and was a once successful singer. Shakti Kumar requests Insia to come to Mumbai for recording a song, but Insia refuses as she has heard a lot negative reviews of Shakti.
One day, Insia sees the husband of her tuition teacher read an article about the secret superstar in the newspaper. Scared that her father will read the article too, she leaves the test to run home and hide the newspaper. Chintan, who has a crush on Insia follows her, and tells her that he knows she is the secret superstar as he recognized her voice. As she had left her test, Insia got very poor marks. Enraged, her father breaks her guitar and beats her mom.
One day, when Farookh was about to take his wife for a party and asks her to wear a necklace, Najma starts making excuses. Realizing that Najma has sold it to buy a laptop, Insia takes her mother to another room to talk to her, but her father overhears them both. Furious, Farookh beats his wife black and blue and asks her to throw the laptop. In a fit of rage, Insia herself throws away the laptop form the balcony and breaks down in her mother’s arms. Watching on the TV about a famous lawyer who fought against Shakti Kumar and won, Insia decides to approach her to get advice on divorce. With no other choice left, Insia accepts Shakti Kumar's proposal and goes to Mumbai, escaping school with help from Chintan.
In Mumbai, Insia is initially unable to sing the party song, as she feels that the lyrics and the beats do not match. She tells Shakti that the song feels like a remix of another song which is never made, and Shakti tells her it's true. He sings the song as he original wrote it, and Insia realizes what a good singer Shakti really is. Shakti tells her that the song is too slow for the generation today, as they all want fast paced party songs. Insia asks Shakti to give the original song a try, and when she sings it, everyone is surprised and moved. The song is then recorded. The secret superstar's fame increases with the song and she is nominated for an award of best female singer.
One's the work was done, Insia requests Shakti to fix a meeting of her and the lawyer. With much reluctance, Shakti fixes a date of next week. Bunking school the same way, Insia meets the lawyer, who gives her certain advice and files for signatures. Once home, her mother scolds her for going to Mumbai without informing anyone. She tells her she can't divorce Farookh as they would have no financial support otherwise. Angry at her mother's refusal, Insia throws a tantrum, but her grandmother reveals how Farookh had wanted to kill her before she was born, and how Najman has struggled to keep Insia alive. Farookh soon reveals that he has got a job in Saudi Arabia, which delights Insia as she would have to bear her father only one month an year, but her happiness is short lived as Farookh tells her that he has fixed Insia's marriage to a Saudi boy and will take his entire family there. He makes tickets for Saudi in order to leave on the day Insia's final examination is over. Chintan and Shakti try to convince Insia to stay, but learning of her mother's efforts to keep her alive, Insia tells them she's got no choice.
On the final day of school, Insia and Chintan spend their last joyful moments together. Chintan reveals that he is going for the award ceremony, and is going to cheer when secret superstar wins. But he feels dejected that Insia won't come. On the day of the last exam, Insia and her family leave for Saudi through two legs, Baroda to Mumbai to Saudi. At Mumbai, at the baggage counter, the clerk tells Farookh that they have one baggage extra. Farookh scolds Najma for carrying the guitar and tells Insia to throw it in the dustbin. For the first time, Najma protests against Farookh as she sees Insia almost break down in tears. When Farookh threatens to slap her in front of everybody, Najma signs the divorce papers, hands it to Farookh and marches out of the airport. Using the phone of a passerby, she tells Insia to call Shakti so that they can arrive to the award ceremony. To the delight of Shakti and Chintan, Insia arrives, still hiding her identity.
The audience tense around when it is time to reveal who is the best female singer. To most people's disappointment, the secret superstar does not win the award. But the winner says that she feels she does not deserve the award because she believes the secret superstar is a better singer than her. She invites the secret superstar to come to the stage and take the award. Finally free of her father, Insia reveals her identity live on television, and dedicates her award to her mother.