More than 100 leaders from five major faiths are at the conference, which was organised by the United Nations agency for children, Unicef.
A Unicef official said religious leaders were uniquely placed to raise Aids awareness in south Asia.
Experts say south Asia could soon surpass southern Africa as the region worst hit by the Aids virus.
The event has attracted Bahai, Buddhist, Christian, Hindu and Muslim religious leaders from Afghanistan, Bangladesh, Bhutan, India, Maldives, Nepal and Pakistan.
Many of south Asia's one-billion people are deeply influenced by religious faiths.