Car festival in Tiruvannamalai

Each ritual comprises four steps: abhisheka (sacred bath), alangaram (decoration), neivethanam (food offering) and deepa aradanai (waving of lamps) for both Annamalaiyar and Unnamulai Amman. The worship is held amidst music with nagaswaram (pipe instrument) and tavil (percussion instrument), religious instructions in the Vedas (sacred text) read by priests and prostration by worshippers in front of the temple mast. There are weekly rituals like somavaram and sukravaram, fortnightly rituals like pradosham and monthly festivals like amavasai (new moon day), kiruthigai, pournami (full moon day) and sathurthi.[33]

The temple celebrates dozens of festivals throughout the year.[34] Four prime festivals, the Brahmotsavam, are celebrated yearly. The most important of these lasts ten days during the Tamil month of Karthikai, between November and December, concluding with the celebration of Karthikai Deepam. A huge lamp is lit in a cauldron, containing three tons of ghee, at the top of the Annamalai hills during the Deepam.[4][35] To mark the occasion, the festival deity of Annamalaiyar circumambulates the mountain. Inscriptions indicate that the festival was celebrated as early as the Chola period (from 850 CE to 1280 CE) and was expanded to ten days in the twentieth century.[24]

Temple car procession during a festival
Every full moon, tens of thousands of pilgrims worship Annamalaiyar by circumambulating the Arunachala hill barefoot.[4] The circumambulation covers a distance of 14 kilometres (8.7 mi), and is referred as Girivalam.[36][5] According to Hindu legend, the walk removes sins, fulfils desires and helps achieve freedom from the cycle of birth and rebirth.  Offerings are made in a string of tanks, shrines, pillared meditation halls, springs and caves around the hill. The circumambulation continues during the rest of the month. On the day of yearly Chitra Pournami, the full moon of the Tamil calendar, hundreds of thousands of pilgrims come from across the world to worship Annamalaiyar. Five temple cars, called ther, with wooden carvings, are used for the procession.

Tiruvoodal is another festival celebrated during the first week of the Tamil month Thai at mid-January of every year. On the morning of Maatu Pongal, between January 15 and 16, Nandi is decorated with garlands made of fruits, vegetables and sweets. The festival deities of Annamalaiyar and Unnamamulai Amman are taken out of the temple to Tiruoodal street to enact the oodal (or love tiff) between the two in the evening.