Razdan started her career in English theatre with John Fowler's The Collector and her Hindi stage career with Bund Darvaze, Satyadev Dubey's adaptation of Jean Paul Sartre's No Exit. She appeared as Sulochana in the hit Doordarshan TV series Buniyad. She also acted in Indian TV serials Saahil, Gaatha and has been a regular on Indian television. In 2002, she produced Aur Phir Ek Din on Star Plus. She has also acted in Bollywood movies. Razdan directed a film called Love Affair. She acted in Meghna Gulzar's Raazi which also starred her daughter Alia in the lead role. Soni played the lead role in the film Yours Truly where she portrayed the character of a lonely middle-aged government employee Mitthi Kumar.