Kajal was born in Mumbai to Vinay Aggarwal, an entrepreneur, and Suman Aggarwal, a confectioner. She has a younger sister, Nisha Agarwal, who is also an actress appearing in Telugu and Tamil films. She studied at St. Anne's High School, Colaba, Mumbai and Jai Hind College, Mumbai. She graduated from K.C. College, Mumbai with a degree in Mass Media. She started her modelling career while she was still in college. She was planning on pursuing MBA in Brand Management before deciding to pursue acting.