Mithan Lam was the daughter of Ardeshir and Herabai Tata. Born in 1898, her father was a manager of a textile mill and had been to Lancashire in 1913 to learn new ideas about the cotton industry. In 1911, on a holiday in Kashmir, Herabai and Mithan met Sophia Duleep Singh, who told them about the suffrage movement in Britain and inspired Herabai to become involved in women's rights.
Mithan was awarded a first class degree in economics from Elphinstone College, Bombay, winning a medal for the highest marks. Through her mother's connections, who was Honorary Secretary of the Women's Indian Association in Bombay, they were invited to go to Britain in 1919 to give evidence to a Royal Commission on Indian Reforms chaired by Lord Southborough.
Mithan spoke to MPs in the House of Commons and at public meetings in London on the issue of female suffrage in India. She then decided to stay on in England, enrolling on a Masters Course at the LSE in October 1919. Her mother remained in England to look after her. In 1920 the Inns of Court were opened for women and Mithan joined Lincoln's Inn in April 1920. She was one of the first ten women to be called to the Bar in 1923.
Upon her return to Bombay in December 1923, Mithan enrolled in the Bombay High Court and became active in womens' organizations and reform. She edited Stri Dharma, the journal of the All India Women's Conference, for five years. She married Jamshed Shorab Lam in 1933.