Nanjeeyar was born Madhava at Thirunarayanapuram, and became so famous a scholar of Vedanta that people called him Vedanti. He followed another school of Vedanta, and was known far and wide for winning debates.
According to tradition, Bhattar came to Thirunarayanapuram and met him in debate. Madhava found in Bhattar's words a truth and a sweetness he had never known, and fell at his feet. Bhattar taught him and returned to Srirangam. Later Madhava took sannyasa and came to Srirangam to serve his acharya. Bhattar welcomed him with joy and called him Nam Jeeyar, "our Jeeyar", and so he became Nanjeeyar.
Nanjeeyar served Bhattar with deep devotion and learned Thiruvaymozhi from him. He wrote a commentary on it of nine thousand padis, the Onbathinayirappadi, and, according to tradition, taught Thiruvaymozhi a hundred times in his life.
The tradition remembers him together with his own disciple. Wanting a fair copy of his commentary, Nanjeeyar gave the manuscript to a young scholar, Nambur Varadar. While crossing the Kaveri, Varadar lost it in the river. He wrote the whole commentary out again from what he had heard from Nanjeeyar, adding finer meanings of his own. When Nanjeeyar saw the new copy he noticed the difference and asked about it. Hearing what had happened, he was not angry but overjoyed, and called him Nam Pillai, "our own son".