Animals should not be released as part of Vesak Day celebrations, the National Parks Board (NParks) warned on Wednesday.
Mr Wong Tuan Wah, director of conservation at NParks, said: "We would like to appeal to the public not to release animals into the wild as it does not guarantee their survival."
This is because these animals used to be kept as pets and are unable to fend for themselves in the new surroundings, he said.
For animals that can adapt to the new environment, Mr Wong added, they may "disrupt the ecological balance" by introducing new viruses, or competing with native species for resources such as food.
The Buddhist festival celebrating the birth, enlightenment and death of Buddha falls on May 13 - next Tuesday.
Mr Yap Kheng Guan, president of the Buddhist Fellowship, also advised devotees not to release animals during celebrations "out of kindness and compassion".
He said: "It is good to refrain from releasing the animals in nature reserves and reservoirs. To do so may subject the released animals to natural predators or cause harm to the eco-system."