Kajal Agarwal made her acting debut in the 2004 Hindi film Kyun...! Ho Gaya Na, in which she enacted a minor supporting role as the friend of Diya, the film’s lead, played by Aishwarya Rai.She then signed in veteran Tamil director Bharathiraja's Bommalattam. The film, however, got delayed and released in late 2008.
In 2007, she made her debut in the Telugu film industry and played her first leading role in Teja's Lakshmi Kalyanam alongside Kalyan Ram, which did not fare well at the box office. Later that year, she appeared in the Krishna Vamsi-directed film Chandamama, which opened to positive reviews and became her first major successful film
In 2010, Kajal starred in A. Karunakaran's Darling alongside Prabhas received favorable reviews from both critics and the audience and became a commercial success at the box office.In August, she appeared in Tamil thriller film Naan Mohaan Alla opposite Karthi. The film is based on a real life incident, opened to unanimously positive reviews.The movie performed well at the box office and was declared a blockbuster. Kajal's final release in 2010 was Brindavanam opposite NTR Jr. and Samantha. The film was critically acclaimed and performed well at the box office.
In 2011, she was paired with Prabhas for the second time in Mr. Perfect, directed by Dasaradh. The film opened to positive reviews, while Kajal won appraisal by critics with Times Of India writing, "What is applause-worthy in the movie is Kajal Agarwal's performance.
She looks great, expresses well and fits into the role perfectly".In May, she appeared in Veera opposite Ravi Teja received negative reviews. She is also making her debut in Kannada in Raju Hasan's Thathasthu opposite Chirag.She is playing female lead role opposite Surya in Maatraan.