Like in the rest of the state, Tamil is the most common language spoken in the town. As per the religious census of 2011, Mannargudi had 90.13% Hindus, 6.82% Muslims, 2.62% Christians, 0.08% Sikhs, 0.01% Buddhists, 0.22% Jains, 0.1% following other religions and 0.02% following no religion or did not indicate any religious preference. As of 2008, a total (34.68%) of the land was used for residential, (2.72%) for commercial, (3.07%) for industrial, (35.81%) for public & semi public purposes including educational and open spaces. As of 2008, there were a total of 28 notified slums, with 12,275 comprising 19.97% of the total population residing in those. Mannargudi has three prominent Hindu temples, namely, Jayamgondanatha temple, Rajathi Rajeswara temple and Raja Gopalaswamy temple. Pamani Naganathar Temple, a padal petra sthalam in Pamani is also located nearby, northerly. Rajagopalaswamy temple is the most prominent landmark in the town. During the Tamil months of "Panguni" (March–April), the most prominent festival of the temple, namely, Pangunith Thirivuzha, is celebrated. Theppothsavam, the float festival, celebrated during the Tamil month of "Aani" (June–July) and Adipooram, the chariot festival, celebrated during the Tamil month of "Aadi" (July-Aug) are other prominent festivals of the temple that attract visitors from nearby villages and towns to Mannargudi. The Nayak kings of the 15th century promoted music in the temples. Instruments like "Mukhavina", "Dande", "Kombu", "Chandravalaya", "Bheri" and "Nagaswaram" were commonly used in the temple service. Haridra Nadhi, the temple tank associated with the Rajagopalaswamy temple, is one of the largest temple tanks in the state. Hindu pilgrims take a holy dip in the tank during festive occasions. Mannargudi has four mosques, located at Theradi, Keela Raja Veethi, Big Bazar Street and Thamari Kuzlam Vada Karai.