Born in 1881, the only son of Radhabai and Ramachandra Rao, Karnad Sadashiv Rao attended Presidency College, and later went to Bombay for Law. In 1909 he returned to Mangalore as a young lawyer and made a name for himself quickly. When he also got involved in social work in 1911, his main mission was the advancement of women. He managed to bring women out of their house with the help of his wife Shantabai, founded the Mahila Sabha. With his wife’s help he started sewing, basket making and such other useful classes for women along with elementary education of women. He supported and encouraged widows to break the custom and join these classes as a part of widow upliftment.
He joined hands with Kudmul Ranga Rao, another social worker among the untouchables of Mangalore, and worked for the upliftment of harijans. As the upper caste temples did not give entry to untouchables, he organized dinner for these untouchables near the temple and sat with them and ate the food to abolish untouchability.
By 1919, he was fully involved in the Indian independence movement, being one of the first from Karnataka to volunteer for Gandhi's Satyagraha movement. He was also one of the key members of the Congress Party and was responsible for expanding the party in Karnataka. He was the soul of Non-Cooperation Movement in the whole of South Kanara District. Sadashiva Rao was also considered as a candidate for the 1937 Provincial elections.
The central library in Mangalore, which was opened in 1967 by the then President of India is named after Karnad Sadashiva Rao.