Kesava Perumal temple has been glorified in 11 verses composed by Nammalwar in the first millennium CE. The architecture resembles those in Kerala. This is also called Aadi Anantam and Dakshina Vaikuntham.

Deity: Aadi Kesava is in a reclining position and faces west. The deity can be seen through three openings in the sanctum. The sanctum was designed so that the rays of the setting sun would illuminate the face of the deity.

Legend: Vishnu vanquished the demons Kesa and Kesi (hence the name Aadi Kesava) and took abode on the coils of Aadi Seshan here at Tiruvattaar. Kesi took on the form of the Tamraparani river. Shiva is said to have taken 12 forms to witness the battle between Vishnu and Kesi, and worship Vishnu. A pilgrimage to the 12 Shiva temples is considered complete after visiting this temple at Tiruvattaar.

Temple: The sanctum faces west, but the main entrance is on the east. The temple stands at an elevation and is surrounded by fort like walls. The towering entrance is reached by steps. There are shrines here dedicated to Adi Kesava, Venkatachalapati and Taayaar. The flagstaff is made of copper and was built by the Travancore royal family.

The circumambulatory passage around the sanctum called Sri Balippuram has 224 granite pillars, each carrying a sculpture of Deepa Lakshmi and none of the images are alike. The balipeetha mandapam has life-sized images of Lakshmana, Indrajit, Nataraja, Vishnu and Bhrama, Rathi and Manmathan. The sanctum has beautiful wooden carvings. Inscriptions from the period of Rajendra Chola are seen in this temple. In front of the sanctum is the Udaya Maartaanda mandapam with ornate woodwork. There is also a carving of Ganesha, and Shiva engaged in tandava. The temple is constructed such that the sun`s rays fall on the feet of the deity`s image from the 3rd to 8th day of the tamil month of Panguni and on the 3rd and 4th days of Purattaasi month.

There is a similarity between this temple and the Anantapadmanabhaswamy temple at Tiruvanantapuram. The deity has an imposing image that of Vishnu in a reclining posture viewed through three doors. The Shiva lingam (Kasi lingam) is near the feet here. Brahma is present on Vishnu`s navel. The image of Garuda here is made of gold inlaid with precious stones and is taken out in procession during vaikasi and aippasi.

Festivals: There are two annual festivals, the first one in the month of Aippasi, where the Teerthavari (Aarattu) is held in the river Tamraparani near the Shiva Tali. The Golden Garuda Sevai is held during both these festivals. Krishna Jayanthi, Vaikuntha Ekadasi, Aavani Tiruvonam, Kalabham in the month of Thai, and the Perunthamritu poojai (Aadi and Thai) on the eve of the summer and winter solstices are some of the festivals celebrated here.