Kajal appeared in a minor role in the 2004 movie, Kyun!….Ho Gaya Na, but got her first major break opposite Kalyan Ram in a Telugu film, Lakshmi Kalyanam, which released in 2007. Directed by Teja, the movie bombed at the box office and failed to garner any positive reviews. Her second release in the same year, Chandamama, directed by Krishna Vamsi was a commercial hit, and her performance was well appreciated.
In 2008, Kajal Aggarwal starred in a few Tamil films like Pazhani, Saroja, and Bommalattam. Pazhani was a commercial success, but the latter two failed miserably at the box office.
Kajal Aggarwal received her first Filmfare Award nomination for Best Actress for the film Magadheera. A historical drama, the movie directed by S. S. Rajamouli starred Ram Charan Teja opposite her. It was a blockbuster and broke several record of the Telugu film industry. She then starred in a rom-com opposite Prabhas. Directed by A Karunakaran, the film was a commercial success and Kajal’s performance established her as one of the most sought after actresses in the south. She then starred in another rom-com, Brindavanam opposite Jr. NTR and Samantha. The movie was a huge success and Kajal received her first CineMAA Award for Best Actress.
In 2011, she paired with Prabhas again in the commercial and critical hit, Mr. Perfect. Her next big release was the Bollywood film, Singham, opposite Ajay Devgn. Directed by Rohit Shetty, Singham was a blockbuster hit and Kajal Aggarwal was nominated for the Filmfare Award for Best Female Debut and the Zee Cine Award for Best Female Debut. In 2012, she appeared as a boxer in Thupakki opposite Vijay. Directed by A. R. Murugadoss, the film was a super hit and went on to become the second film to cross the 100cr mark. Some of her next releases included Naayak, Special 26, Baadshah, Govindudu Andarivadele, Brahmotsavam, Sardaar Gabbar Singh.
In 2016, Kajal starred opposite Randeep Hooda in a romantic drama film Do Lafzon Ki Kahani, directed by Deepak Tijori.