PMK leader Anbumani Ramadoss on Friday took oath as a member of Rajya Sabha.
Ramadoss, MDMK founder Vaiko and two candidates each from the AIADMK and the DMK were elected unopposed to the Upper House from Tamil Nadu earlier this month.
When the House met for the day, Chairman M Venkaiah Naidu called for oath or affirmation of the new members.
Ramadoss, who took oath in Tamil, was warmly greeted by Naidu. Members thumped desks to welcome him.
New AIADMK Rajya Sabha members A Muhammathjohn and N Chandrasekaran and DMK members N Shanmugam and P Wilson as also Vaiko had taken oath on Thursday.