The main one is the Vrishchikoltsawam, which is conducted annually in the month of Vrishchikam (November–December), kicking off the Ulsava season in Kerala.

[citation needed] Traditionally, Thrikketta Purappadu day (fourth day of Vrishchikotsavam) sees Poornathrayeesa in opulent majesty, ensconced in a jewel-studded golden accoutrements atop a stately tusker surrounded by 14 elephants while devotees make their offerings in golden pots specially taken out from the temple’s kallara (treasure vault) for the occasion.

[4] Traditions say that Vishnu offered the idol of Poornathrayeesa to Arjuna when he sought the help of the god to give rebirth to the ten children of a Brahmin.

[citation needed] Ganesh, who was attracted by the holiness of the ancient Vedic village, Poornavedapuram (now Tripunithura), tried to occupy the place for himself.

A Valia Vilakku is situated in front of the idol; people say that the burnt oil of this traditional lamp contains medicinal value.

A major fire occurred in 1920, which destroyed much of the original structure, particularly the sanctum sanctorum which was built extensively in wood.

The birthday of Poornathrayeesha falls on "Uthram" Nakshathra of the Malayalam month Kumbham (February–March), which is preceded by Para Utsavam, where people give special offerings to the temple.

Every year in August–September, there is another festival called Mooshari Utsavam in commemoration of the sculptor who had moulded the divine image of Poornathrayeesan.

It is believed the sculptor himself merged with the divine to give life to the amazing mould of Poornathrayeesha, which is still used in the sanctum.