Aur Pyaar Ho Gaya revolves around a progression of love between the two protagonists, Bobby Oberoi (Bobby Deol) and Ashi (Aishwarya Rai). Ashi is a free-spirited woman, in her early twenties, who has no plans to get married soon. Her father, Kailashnath (Anupam Kher), is traditional and believes important things in life, such as marriage, should adhere to the family's customs. He expresses his desire of marriage for Ashi and tells her he has a guy picked out for her, Rohit Malhotra. Ashi gets enraged at first, and then agrees to the marriage on the condition that she be allowed to meet him anonymously and observe his character and personality. Ashi's father obliges and Ashi is soon off to Europe to meet Rohit Malhotra. Ashi pursues her search of Rohit in Switzerland.
While she is there, she meets a man who continuously teases her and happens to be staying in the room next to her. This man is Bobby Oberoi. He dotes on and flirts with her, but she doesn't reciprocate. She becomes frustrated in her failed attempts to find Rohit and Bobby over hears that she is searching for a man named Rohit Malhotra. To win Ashi's heart, Bobby lies and tells her he is Rohit.
Gradually, they fall in love and she finds out his real identity. Upon their return to India, the families meet and agree for the marriage. Bobby's mother (Beena Banerjee) is the manager of the bank where Kailashnath deposits money. The police visit the bank to investigate a recent business scandal. It turns out that Kailashnath is part of the scandal and Bobby's mother has no option but to cooperate with the police, even though it might strain relationships with her soon to be family-in-law. Subsequently, Kailashnath is arrested. For him, that was a humiliating event. He furiously cancels Ashi's marriage to Bobby. Furthermore, he arranges Ashi's marriage to Rohit. After a whole other twist to the film, it ends with Ashi marrying her soulmate.