Ramachandra Rao, was responsible for mentoring Ramanujan on seeing his prowess in research, and provided financial aid, took care of his daily needs and got him a clerk's job at the Madras Port Trust.

As a student, Rau wrote an essay under Hardy's guidance that fetched him the coveted Smith Prize in 1917, following which he was also elected a fellow of King's College.

Rau published several papers, primarily in three fields: summability of series, theory of functions of a complex variable and sums of an even number of squares.

Among the first papers he wrote after his return was on the subject of the Riemann zeta function, and the technique devised by Rau was found to have wide applicability in other problems of number theory.

Ananda Rau taught several well-known mathematicians, including Subrahmanyan Chandrasekhar, K. S. Chandrasekharan, S Minakshisundaram, C T Rajagopal, C S Venkitaraman and M V Subbarao.