UNICEF says an estimated 12,000 Nepalese children are trafficked to India every year, but since the two catastrophic earthquakes earlier this year the threat is even higher.
Girls not recruited into prostitution face being sold as domestic slaves, and boys are taken into forced labour.
Chief of Child protection for UNICEF in Nepal, Virginia Perez said many parents, faced with poverty, are tricked into parting with their children.
"Children are unnecessarily separated from their families and placed in institutions with a fake promise of ensuring access to education and health and other services."
"The reality is that they are being exploited by privately run care-homes and orphanages that don't necessarily care about the best interests of the child but want to make a profit."
Ms Perez says UNICEF has already helped to prevent 513 potential cases of trafficking since the earthquake in Nepal.
A number of measures were put into place following the earthquake to manage the risk of child trafficking, including a halt on inter-country adoption and the registration of new orphanages.
NGOs including UNICEF have also been patrolling roads to identify children travelling with adults, checking they have the correct documentation.
Ms Perez says radio messages, sent out several times day, since the earthquake have been effective in educating families about the risks of trafficking.
"Before the earthquake they had never thought that sending a child to a care home would be bad for the child," she said.
The charity also stepped up it's warning to well-intending Westerners planning to volunteer at Nepalese orphanages without the necessary skills or training.
"It can actually do more harm to children. It can create a continued sense of abandonment. And it keeps the private business of these orphanages going," Ms Perez said.