Sree Mahavishnu temple is located at Thennilapuram on the Erattakulam - Vaniyampara Road adjoining Palakkad – Thrissur National Highway in Palakkad district. The main deity worshipped in the temple is Vishnu Bhagavan. The temple has a circular sanctum sanctorum or vatta sreekovil.
The annual pratishta festival in the temple is held in Kumbha Masam.
The Upa Devatas worshipped in the temple are Ganapathy, Sree Dharmasastha, Hanuman Swamy, Naga Devatas and Durga Parameswari.
The important rituals and festivals in the temple are Gokulashtami (Sri Krishna Janmashtami) and Naga Pooja.
Thennilapuram Vishnu temple is associated with the nearby Kunnekkattu Bhagavathy temple. The belief is that the presence of Mahavishnu was felt here before the presence of Bhagavathy. Therefore devotees first have darshan in Thennilapuram Vishnu temple before visiting Kunnekkattu Bhagavathy temple.