A high court on Monday found Bellana Panniyaloka guilty of grave sexual abuse of a 16-year-old girl in 2001, and gave him the maximum 20-year prison term.
Moments later, the monk drank from a bottle he had concealed in his saffron robes. He then collapsed and was rushed to the hospital, where he died Tuesday.
"He had consumed a large quantity of insecticide and died of poisoning," said Hector Weerasinghe, director of the Colombo National Hospital.
Reports of child abuse by Buddhist priests have increased in recent years, but this was the first conviction of a monk on abuse charges.
About 70 percent of Sri Lanka's 19 million people are Buddhists, and monks play a major role in molding the island's political and social fabric.
High Court Judge Rohini Perera, who also fined Pnniyaloka US$1,000, said at the sentencing Monday that the maximum prison term was being imposed to safeguard Buddhism.
Perera called the monk's offense "shocking and disgraceful," and said it is unacceptable for children to go unprotected at places of worship.
The court heard testimony from the teenage victim saying she was abused when she attended classes at the temple where the priest resided in Nugegoda, just outside the capital Colombo.
Panniyaloka had threatened to expel the girl from the classes if she told anyone of the abuse but she told her school principal, court official N.K. Siripala said.
By Shimali Senanayake By Shimali Senanayake