As a result of Dwarakanath Ganguly's fight for women's emancipation, Sarala Das and Kadambini were considered eligible in 1877 to sit for the entrance examination for Calcutta University. Ultimately, only Kadambini took the exam and passed in the second division. In 1883, Kadambini Basu and Chandramukhi Basu, a Bengali Christian from the United Provinces, received their BAs from Bethune College, becoming the first women graduates in the British Empire. Kadambini now decided to study medicine at the University.
Shortly after entering the medical college in 1883, Kadambini, only 21 years old, married her teacher and mentor Dwarakanath Ganguly, a 39-year-old widower. The marriage was apparently a happy one, based as it was on a sense of equality and meaningful companionship.
Kadambini passed in all the written papers for the final examination, but failed in one essential component of the practicals. In 1886, she was awarded a GBMC (Graduate of Bengal Medical College) degree, which gave her the right to practise. She thus became the first Indian woman doctor qualified to practice western medicine. Earlier, in 1884, Kadambini was awarded a government scholarship of Rs 20 a month for women medical students. She established a successful private practice and in 1888 was appointed to the Lady Dufferin Women's Hospital on a salary of Rs 300 per month.
Soon after the foundation of the Indian National Congress in 1885, Dwarakanath started agitating for women's representation at the annual sessions. As a consequence, six women including Kadambini attended the 1889 session. She moved a vote of thanks and was hailed by Annie Besant for being 'a symbol that India's freedom would uplift India's womanhood'. A conservative section of Hindu society launched a slander campaign against her and though she combined her role of a doctor and a good wife and responsible mother very successfully, she was indirectly called a whore by the conservative journal Bangabasi in 1891. Kadambini won a libel case against the editor of the journal, Mohesh Chandra Pal, who was fined 100 rupees and also sentenced to six months' imprisonment. In 1893, Dwarakanath sent Kadambini to Edinburgh for higher studies in medicine.
Kadambini combined her work as a doctor with social philanthropy and political activities. She was one of the organisers of the Women's Conference held in Calcutta in 1906. In 1908 she also organised and presided over a meeting organised in Calcutta to express sympathy with Satyagraha workers of Transvaal, South Africa. She soon started an association and collected money to help the workers. In 1914 she presided over the meeting of the Sadharan Brahma Samaj, held in Calcutta in honour of Gandhi during his visit to Calcutta.
Kadambini was aware of the exploitation of tea garden labourers by their employers and supported the views of her husband who condemned the existing system of recruitment of labourers in the tea gardens of Assam. In 1922, a year before her death on October 3, 1923, she accompanied poet Kamini Roy on a visit to Bihar and Orissa to inquire into the conditions of women labourers employed in the coal mines on behalf of an Enquiry Commission set up by the Government.