In 1998, Mukerji starred opposite Aamir Khan in Vikram Bhatt's action film "Ghulam", her first commercial success. Though her role in the film was small, the song "Aati Kya Khandala" earned her public recognition. Due to Mukerji's husky voice, Bhatt had someone with a higher pitched voice dub her lines; Mukerji stated that it was done as her voice "did not suit the character". In the same year, Karan Johar cast her opposite Shah Rukh Khan and Kajol in his directorial debut "Kuch Kuch Hota Hai". The role was originally written for Twinkle Khanna, but when she and several other leading ladies rejected it, Johar signed Mukerji on the insistence of Khan and the filmmaker Aditya Chopra. She played Khan's character's love interest and later wife, Tina who dies after giving birth to their daughter. Johar had originally intended to dub Mukerji's voice, but she improved her diction and eventually provided her own voice. Reviewing the film for "India Today", Nandita Chowdhury wrote that it was "the gorgeous Rani who steals the show. Oozing oomph from every pore, she also proves herself an actress whose time has come". "Kuch Kuch Hota Hai" proved a breakthrough for Mukerji; it had earnings of over to emerge as the year's top-grossing Hindi film, and won eight Filmfare Awards, including Best Supporting Actress for Mukerji. Following this, she had starring roles in "Mehndi" (1998) and "Hello Brother" (1999), critical and commercial disappointments that failed to propel her career forward.