Kapoor was initially approached to make her debut in Rakesh Roshan's Kaho Naa... Pyaar Hai (2000) opposite Hrithik Roshan. However, after several days into the filming, she abandoned the project. She later explained, "It was probably destined that I was not to be in the film. After all, it was a launch for his son (Rakesh Roshan). The whole focus was on the boy. Now I am glad I did not do the movie."
Her career commenced with J.P. Dutta's moderately successful Refugee (2000) opposite Abhishek Bachchan. Set during the India-Pakistan conflicts, the film centers on a young man, Refugee, who carries out the illegal activity of taking civilians to Pakistan and forth. Kapoor played the role of Naaz, a Bangladeshi girl who falls in love with him while migrating to Pakistan; her performance won her critical acclaim. Taran Adarsh from indiaFM wrote, "Kareena Kapoor has a magnetic personality, which will make the viewer fall in love with her instantly. On a scale of 10, Kareena's performance deserves 9 marks, dialogue delivery 8 and overall personality 10. What surprises you is the ease with which she emotes the most difficult of scenes, that too against experienced performers. There's no denying the fact that she is a natural performer who is very camera friendly." Earning Kapoor her first Filmfare Award in the Best Female Debut category, the film eventually went on to became the fifth highest grossing film of the year.
Kapoor started her year successfully in 2001, as her first film, Satish Kaushik's Mujhe Kucch Kehna Hai opposite Tusshar Kapoor surfaced as one of the biggest hits of the year. Though her subsequent films Yaadein and Asoka did poorly at the box office, her performance of a princess in the latter was well received, earning her first nomination for Best Actress at the Filmfare. Later that year, she starred in Abbas Mustan's thriller Ajnabee. Although the film tackled an audacious theme of couple swapping, which critics thought the Indian audience would find hard to absorb and identify with, the film fared reasonably well and became one of the highest grossing films of the year.
Kapoor's last release of the year was Karan Johar's drama Kabhi Khushi Kabhie Gham. Consisting of a multi-starrer cast that included Amitabh Bachchan, Jaya Bachchan, Shahrukh Khan, Kajol and Hrithik Roshan, the film became the second highest grossing film of the year and the year's biggest hit overseas. Her performance as a cosmetic beauty was applauded and earned her a nomination for Best Supporting Actress at the Filmfare ceremony. Taran Adarsh noted, "Kareena Kapoor is one of the main highlights of the film. She provides the much-needed fun and entertainment in the second half; her performance will be loved by the youth. Playing a cosmetic beauty to the hilt, she is simply adorable." These successes and accomplishments established her as one of the industry's most successful stars.
In 2002, she starred alongside Hrithik Roshan and Rani Mukerji in Kunal Kohli's directorial debut Mujhse Dosti Karoge! (2002), her first film with Yash Raj Films, one of the biggest production houses in Bollywood. The film was a critical and commercial failure in India, though fared well overseas, especially in the U.K. Portraying a love triangle between three childhood friends, the film saw Kapoor playing a young and modern girl, Tina. Her performance was not well received; Sukanya Verma from Rediff.com criticized her, "Kareena Kapoor is inconsistent. The actress looks ravishing in every frame, but she repeats her smug Poo act (Kabhi Khushi Kabhie Gham) to an annoying effect here."
Sooraj R. Barjatya's love-triangle Main Prem Ki Diwani Hoon, co-starring Hrithik Roshan and Abhishek Bachchan was Kapoor's next project in 2003. Produced by Rajshri Productions, the film failed to do well in India, but once again, was a hit overseas. Kapoor's performance of Sanjana, the cynosure of two men was criticized, "Kapoor was annoying in her role as Sanjana - a role we have seen her act many times before in movies such as [Karan] Johar's K3G, [Subhash] Ghai's Yaadein and more recently [S J] Suryah's Khushi." Following this, Kapoor was generally criticized by critics for enacting repetitious kind of roles in her films, who were expressing that she was indeed in danger of becoming typecast, which was fundamental in her attempting a diversity of more adventurous roles in the years following.
In 2004, Kapoor began working with independent directors and doing more serious roles that brought her critical acclaim rather than commercial success. Her role of a prostitute in the 2004 film, Chameli proved to be a turning point in her career and made critics take notice of her once again, earning her the Filmfare Special Performance Award. Film critic Subhash K. Jha wrote, "Kareena goes way beyond anyone's expectations, including most decidedly her own, to deliver an all-time great performance, on a par with Nargis in Mehboob Khan's Mother India (1957), Meena Kumari in Sahib Bibi Aur Ghulam (1962) and Shabana Azmi in Mahesh Bhatt's Arth (1982). Kareena flashes an intuitive brilliance that comes to movies very, very rarely indeed."
Following Chameli, Kapoor starred in Govind Nihalani's critically acclaimed Dev, which dealt with the historical events of the 2001 Gujarat riots. Modeled after Zahira Sheikh, a key witness in Vadodara's Best Bakery case, Kapoor played Aaliya, a middle-class Muslim girl, a victim of these riots. Her performance earned her a Filmfare Critics Award for Best Performance as well as several nominations for Best Actress at various award ceremonies. Taran Adarsh noted, "Kareena Kapoor is first-rate. Sporting a deglamorized look, the actress takes a giant leap with this film. Her scene with Amitabh Bachchan [when the latter asks for witnesses to come forward] is an example of superb acting." In that same year, Kapoor played her first negative role in Ken Ghosh's Fida. Although the film failed to do well, she received positive reviews for her performance, with one critic writing, "Kareena has finally moved beyond Poo in K3G and has come into her own. She has portrayed the parts where she is racked by guilt very well." Her next releases that year included the thriller Aitraaz, which was moderately successful, and the comedy Hulchul, her first box office success since 2002.
This was followed in 2005 by Dharmesh Darshan's drama, Bewafaa, alongside Anil Kapoor, Akshay Kumar and Sushmita Sen. Kapoor played the female lead of Anjali, a girl who marries her sister's husband after her death. Unsatisfied with her married life, she sets on a relationship with her previous lover. The film received mixed reviews by critics and so did Kapoor's performance. Taran Adarsh wrote about her performance, "This is Kareena's film all the way and the talented actress knows how to absorb a meaty role like this. She looks stunning, emotes with complete maturity and delivers a knockout performance" whilst another noted, "Kareena...speaks in undertones and looks half-dead.
36 China Town was Kapoor's first release in 2006 followed by Chup Chup Ke. Both films managed to do moderately well at the box office. However, she was mostly noticed with her portrayal of Desdemona in the Indian adaptation of William Shakespeare's Othello, Omkara. Directed by Vishal Bharadwaj, the film co-starred Kapoor alongside Ajay Devgan, Saif Ali Khan, Vivek Oberoi and Konkona Sen Sharma. Her performance was praised, earning her a Filmfare Critics Award for Best Performance and a Star Screen Award for Best Actress. Critic Taran Adarsh wrote, "Kareena delivers an award-worthy performance. She looks gorgeous even without makeup." In the same year, she won favorable reviews for her item number in the hit movie Don - The Chase Begins Again.
Kapoor's only release in 2007 was the comedy-romance hit Jab We Met opposite Shahid Kapoor. Directed by Imtiaz Ali, the film tells the story about two people with contrasting personalities meeting each other on a train and how they learn to deal with the situations they face in life. Kapoor played the female protagonist Geet Dhillon, an annoying talkative Sikhni girl from Bhatinda who lives life to the fullest. The film was well received by critics and Kapoor's performance was praised in particular. Rajeev Masand from CNN-IBN noted, "Uninhibited and spontaneous, Kareena Kapoor is the soul of this picture, its biggest strength, as she brings alive her character with not just those smart lines, but with the kind of candor actors seldom invest in their work. I can't think of a greater compliment to pay her than to say with full confidence that no actress could play Geet better than Kareena has."
