In 1955, Nainar Sundaram started practice in civil and criminal side in the Madras High Court.
On 4 January 1978 he was appointed an additional Judge of Madras High Court.
Nainar Sundaram was elevated to the post of the Chief Justice of Gujarat High Court on 15 June 1992.
[1] Thereafter he became the Chief Justice of the Telangana High Court in December 1993.
[2][3] Justice Nainar Sundaram was appointed the first Chairperson of State Human Rights Commission Tamil Nadu after retirement.