Thirumullavaram Mahavishnu Temple is located on the seashore at Thirumullavaram, around 5 km from Kollam Railway Station. The annual festival in the temple begins on Atham nakshatra with kodiyettam and ends with arattu on Thiruvonam nakshatra in Meenam month (March - April). The shrine observes the annual Karkidaka Vavu Bali and Pitru Tarpanam on the Vavu or Amavasya day in Karkidakam month. Hundreds of people arrive on the seashore and pay respect to depart souls in their family. Special arrangements are made by temple management for Bali Tarpanam throughout the year especially during Vavu (no moon day or Amavasya)
Vishnu and Shiva have equal importance in the Thirumullavaram Mahavishnu temple. Vishnu faces east and Shiva faces west. The sreekovil of Vishnu is circular – vatta sreekovil.
There is Parvati Devi, Dharma Sastha, Murugan, Bhuvaneshwar and Rakshas in the temple of Shiva.
This is one among the 108 Vishnu temples in Kerala. It is believed that the sea had engulfed the original temple and the current temple was constructed later.
It is believed that the Vishnu murti in the shrine was the Thevara murti of Kulasekhara Perumal who ruled the area with Kollam as his capital.
Thila Homam for pitrukkal is performed in the temple.
Although, the temple is located near the seashore, the water in temple well and temple pond is not salty but normal water.