Born on 2nd March 1932 in Mumbai, Purnima's father Ram Sheshadri Ayangar was a Tamil Brahmin who used to handle accounts at Manmohan Desai's film distributor father Kikubhai Desai's office. Purnima's mother was from a Muslim family of Lucknow. At home other than her parents there were five daughters (including Purnima) and a son. In the 1930's decade, Purnima's eldest sister Shirin Banu had also worked in films like Bambai Ki Sethani (1935), Passing Show (1936), Khwab Ki Duniya (1937), State Express (1938) and Bijli (1939). Shirin Banu was the mother of director Mahesh Bhatt and producer Mukesh Bhatt as well as the grandmother of actresses Pooja Bhatt and her step sister Alia Bhatt. According to Purnima that era's well known director Raman B. Desai, who was also their neighbor, had offered Purnima 'Radha's' role in his Guajarati film 'Radheshyam'. Purnima was still in school at that time. For the film, her elder sister Shirin Banu, gave her the alias 'Purnima' in place of her real name 'Meher Bano'. The film 'Radheshyam' was released in the year 1948 and at that time Purnima was merely 16 years old. According to Purnima, "My first Hindi film was Kidar Nath Sharma's Thes (1949), where I was playing the second lead." Featuring Bharat Bhushan and Shashikala Jawalkar in the main roles, this film was released in the year 1949. According to the senior film historian Shri Harish Raghuwanshi, in the year 1948 i.e. a year before Thes (1949), Purnima had acted in two Hindi films 'Manager' and 'Tum Aur Mai' and in 1948 other than 'Radheshyam' she had also worked in Director Raja Yagnik's Gujrati film 'Saavaki Maa'. After Thes (1949), Purnima saw two more releases in 1949 viz. 'Narad Muni', and Patanga (1949), where she was seen playing the second lead in both the films. While Raman B. Desai,'s Gujarati and Hindi bilingual film 'Narad Muni' and Kidar Nath Sharma's Thes (1949) could not create much box office magic, Producer Bhagwan Das Varma's film Patanga (1949) proved to be very successful. Composed by C. Ramchandra, two songs of this musical hit film 'dil se bhula do tum hamein' and 'o jaane waale tone armanon ki duniya loot li' were filmed on Purnima and after the film's release Purnima's schedule became very hectic. Punima's second husband Bhagwan Das Varma, whom she married in 1954, was a famous Producer-Director of his time who had many successful films like Patanga (1949), Sagai (1951), Badal (1951), Aurat (1953), Parbat (1952) and Pooja (1954) under his banner of 'Varma Films'. Bhagwan Das Varma passed away in 1962. According to Purnima, she acted in almost 200 films in a career spanning more than five decades. Her only son worked in Air India. Shakila, Saira Banu and Dulari were her friends. Since Shakila, Saira Banu stayed close to Purnima's house they kept meeting quite regularly.