Preeti was born on May 17, to actor Kumudlal Kunjilal Ganguly alias Ashok Kumar and RattanBai. She was their only child. Her paternal grandfather was an Advocate, Kunjilal, and her grandma, Ghouri Rani Devi (nee Bannerjee), the sister of classical singer, Dhananjay Bannerjee. Her uncles are Anoop and Kishore Kumar, both well-known actors/singers in their own rights. She is cousin of Shomu, Joy and Deb Mukherjee. Shomu is actress Tanuja's husband, and father of actresses Kajol and Tanisha, as well as father-in-law of Ajay Devgan. Her aunts, through marriage to uncle Kishore Kumar, include Madhubala, Yogeeta Bali, & Leena Chandavarkar.

Following in the footsteps of her dad and uncles, she debuted in Parinay in 1974. She mostly played roles that provided a comical relief to viewers, in particular those of an overly healthy woman. Her career spanned from 1974 through to 1988 in a total of about 30 movies. After losing weight she made a come-back in 'Tum...Ho Na' and 'Aashiq Banaya Aapne' in 2005.

When she started to shed pounds from her body, she virtually stopped receiving offers, so much so that she decided to open an Acting School in Bombay, where she hopes to find talent to act in her TV series. Her dad used to teach Film Appreciation and actress Shabana Azmi also made teaching appearances. The acting course is approximately 6 months long, and can cater to a maximum of 15 students. Most of the students who enrolled in her school are from upper middle-class families.

She is often misquoted as being married to popular actor-comedian, Late Deven Verma, but its not correct. Actually Late Deven Verma was married to Preeti's elder sister Roopa Ganguly ( again not to be mistaken by the famous TV actress Rupa Ganguly who played the role of Draupadi in the Mega Serial "Mahabharat" )Thus He was Preeti's Brother-in-Law.