In Thailand, Buddhist monks attended a ceremony at Wat Dharmmakaya in Pathum Thani, on the outskirts of Bangkok.
The Fo Guang Shan Association here had a novel way to celebrate Vesak Day: It held a series of environmental activities together with its usual spiritual programmes.
The association said it is trying to raise awareness on environmental conservation - which resonates with Buddhist teachings.
The festivities include a pledge-taking by Buddhists to make Singapore a more environmentally-friendly home. There will also be an exhibition of objects made out of recycled items.
It is believed that by performing good deeds on Vesak Day, the merit earned will be multiplied many times over.
In Sri Lanka, for instance, prison authorities released 858 prisoners serving time for minor offences.
In Singapore, a group of 70 people set free over 2,000 fish into the ocean.
The group had gone to a kelong off Changi and bought over 400kg of fish - for about S$6,000 - which were meant to be sold to restaurants for consumption.
The National Parks Board had warned earlier against releasing animals on Vesak Day, so as to not disrupt the ecological balance as well as threaten the survival of the released animals. According to animal rights activists, as long as the animals are returned to their natural environment, they will be all right.