Kajal 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.[4][5] 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.[6]
In 2008, she had her first Tamil film release, Perarasu's action entertainer Pazhani, co-starringBharath. Following this film, she had two more Tamil releases that year with Venkat Prabhu’s comedy-thriller Saroja, in which she did a guest appearance, and Bharathiraja’s investigative thriller Bommalattam. Although the former went on to become a commercial as well as a critical success, both films failed to boost her career as her roles were too insignificant.[7] Both her Telugu releases, Pourudu and Aatadista opposite Sumanth and Nitin, respectively, neither received positive reviews nor were successul at the box office.
In 2009, she had four releases, she first starred in another Tamil film Modhi Vilayadu, which garnered mixed reviews and was a financial failure, following which she appeared in the high-budget Telugu historical drama Magadheera, which saw her essaying double roles for the first time. The film, directed by S. S. Rajamouli, received universal critical acclaim, while Kajal, particularly, was praised for her portrayal of a princess in the film. Rediff wrote that she "was quite a surprise package, [...] sweet and charming and looked like an 'ethereal' princess. She carries off both the roles fairly well",[8] while NDTV cited that "Kajal Agarwal is also an asset to the film. She is very apt for the character of the princess. Besides filling the glamour slot, she has proven that given a chance, she too can give an excellent performance".[9] The film was also highly commercially successful and broke several records,[10] emerging as the highest-grossing Telugu film of all time.[11][12][13] Following Magadheera’s phenomenal success, Kajal became one of the most sought-after actresses in the Telugu film industry, catapulting her into the main foray of lead Telugu actresses.[14][15] Her subsequent releases Ganesh Just Ganesh and Arya 2 received mixed reviews from critics, while her performance garnered positive feedback