In 1924, Rajamannar started his law practice joining his father's chambers.In 1944 P.V. Rajamannar was appointed Advocate-General in succession to Sir Alladi Krishnaswami Aiyar.
Later in 1945, P. V. Rajamannar was appointed as Judge of Madras High Court and in 1948 Rajamannar became the first Indian to be elevated as Chief Justice of Madras High Court [REF].