Rahul Malhotra (Aamir Khan) is the manager of a garment company. The company has a pending order of two lakh shirts to Mr Bijlani which they have not delivered. He is also the guardian of his dead sister's mischievous kids: Sunny, Munni, and Vicky. The kids are rowdy to him and, as a result, he locks them up in a room. At night, the children escape through the window and head for a mela happening in the city which their mama (Rahul) had promised but refused due to their behaviour.
On the other hand, Vyjanti (Juhi Chawla) is the daughter of a music lover. He wants her daughter to get married to an Iyer clan music legend who happens to be have girlish behaviour. She is upset because she does not want to marry someone whom she calls a "clown". Just like the kids, Vyjanti gets locked up and also escapes ending up in the mela. She meets the three kids and they become friends. Vyjanti explains that she has no home as of now so the children readily invite her to stay with them.
One night, a cheeky thief, Mr Mishra (Rahul's company executive) and an obsessive crazy-lover type college student, Maya, end up at his home. Mishaps occur where Maya (the young woman who loves Rahul) and the thief escape, leaving Mr Mishra behind. He explains that he had come to see the children earlier; there were not three but four children and proves himself right. Rahul realises his mistake and asks Vyjanti who she was and that she had been in his house for two days without him knowing it. She explains why she had come here, adding other fake, sad family stories. Due to his pity for the girl's "fake stories," Rahul gives her a job as the children's governess at 200 rupees a month. In the morning, Vyjanti explains to Rahul that she cannot cook which drives Rahul in confusion. When in the kitchen, Vyjanti accidentally burns her fingers by touching a hot water pot. When Rahul applies a soothing cream to her hands with the children behind him watching, she makes blushing eyes and smiles. Rahul notices and it is obvious that she was beginning to fall for him instantly.
Vyjanti's father is worriedly looking for his daughter everywhere. Rahul and the children (especially Vicky) have other problems but soon become accustomed to each other. They all enjoy their times. Soon, Vyjanti begins loving Rahul deeply but can only express it with eyes and actions but no words (as in the song "Kash Koi Larki").
Maya, on the other hand, is Biglani's daughter. She asks her dad to forgive the debt of the company and ask for Rahul's hand in marriage. Rahul deeply thinks of this and approves, not knowing of Vyjanti's hidden feelings for him. He does so to think of the benefit of the children. One night, Maya is invited by Rahul to dinner at home. Maya is ill-greeted by the children and calls Vyjanti "nockrani". Neither the children nor Vyjanti know that Rahul is about to get engaged to Maya. Maya expresses to Rahul that they will need a housegirl after marriage. Suddenly, Vyjanti looks and moves away toward the kitchen in shock. Rahul apologizes about the fact that he should have told the kids and her about the marriage plans. Vyjanti replies, disraught, that she should have known she is only a servant. Vyjanti is really disheartened and cries (this is shown in the song "Woh Meri Neend").
The engagement takes place at a bar while, at home, Vyjanti explains to the kids that she loves Rahul and wants to marry him. The kids come up with a plan to stop the occasion. Arriving at the party, the three create a drama and Rahul forcefully takes them home. At home, Rahul is inquisitive and frustrated about what happened and scolds Vyjanti. Vyjanti cannot hold her feelings back and expresses to Rahul that she loves him and cannot afford to see him getting married to someone else.
In the morning, Biglani comes with his daughter with a second chance to Rahul. Rahul explains saying that Vjyanti was not only someone ordinary, but like a mother, sister and a friend to the children. Biglani angrily lectures Rahul that he is making a very big mistake. Secretly, the mischievous kids alongside Vjyanti bring fruit and throw it at the two. Happily Vyjanti kisses Rahul on the cheeks and lips quickly (this is where the blockbuster song "Ghunghat Ki Aarse" comes).
Rahul realizes what he did and asks his workers to work overtime to make up for the orders just for him. A successful two lakh shirts are made and ready to be delivered to Biglani. During the delivery, Biglani arranges for some men dressed in police uniforms to capture the truck. Everyone is shocked when the order does not arrive on time during the auctioning of the house, a plan by Biglani to ruin Rahul. Luckily, Rahul and the others meet the "cheeky thief" at a police station who knows about the whereabouts the gang. When they get there, Rahul gives the gang a good showtime but unfortunately the tyre of the delivery truck gets punctured on the journey. This was the time where Mr Mishra had to show his talent he got from Japan when a bus full of Japanese people was passing in front. The shirts are quickly loaded and taken to their house before the auctioning was suppose to finish. The judges listen to Rahul and claims Biglani as a fraud. He is again thrown eggs at alongside his daughter and other personnel.
They are all very happy now but still one thing remains unsolved: Vyjantis dad's disapproval of getting her married to anyone apart from the Iyer clan. All female workers from the factory, Rahul's colleagues and the children request continuously. At the end, he accepts but with a small condition: that the wedding should be a South Indian-style one. This was no problem to anyone so they all shouted in joy. Vyjanti and Rahul get married and thus the story comes to an end.