The moolvar of the temple is Lord Siva. It is believed the temple has both Pallava and Chola architecture. It is also found from the Inscriptions that the shrine of Tripurasundari Amman in the 11th century during the period of Rajendra Chola.
Lord Marundeeswarar is known so because he taught sage Agastya about some magical medicine. Since then the Marundeeswarar temple has been a place of worship for people with diseases and various problems with their health. It is said that even The Sage Valmiki, who wrote The Ramayana, came here to The Marundeeswarar temple to worship The Lord. Sage Valmiki was said to be blessed here. After this incident, this place was to be known as Thiruvalmikiyur, after a long period of time, the name gradually changed to Thiruvanmiyur. There is a place present in Thiruvanmiyur called Valmiki Nagar in his honour.
There is also a temple built for Sage Valmiki in the middle of the East Coast Road, very close to the Marundeeswarar temple. The lingam for which Lord Hanuman performed pooja, The lingam(meenakshi sundareswarar) that cured the curse of Lord Indra, the Lingam for which Saint Bharadwaja performed pooja are present here. Markandeyar performed a penance and prayed to lord Shiva here, Lord Brahma is believed to have conducted a festival here for lord Shiva. There is a story that Vishnu worshipped Shiva with his family here to get a son, but he forgot to worshipp parvati devi who cursed his son to die at once after birth.