[citation needed] Sastri began his career as an advocate in the Madras High Court in 1914 and practised for some time, gaining repute as having special expertise in tax law, particularly with Chettiar clients.

In 1922, he was appointed standing counsel to the Commissioner of Income Tax in recognition of his abilities in this field; he held the position until his elevation to the Bench on 15 March 1939.

During this time, he, along with Sir Sidney Wadsworth notably tried complicated cases that followed after the passing of the Madras Agriculturists Debt Relief Act.

[2] He replaced his close friend Sir Srinivasa Varadachariar, who had been appointed to the Federal Court of India.

[2] His great grandsons are Avanidhar Subrahmanyam, a Distinguished Professor at the University of California, Los Angeles, and Dr. Mandakulutur Subramanya Ganesh, Head of Oncology, Vydehi Institute of Medical Sciences, Bengaluru.