In a ceremony in Tonga on Tuesday, Mr Taufatofua was signed up as Pacific Ambassador by the UN Children's agency, UNICEF.
The former youth counsellor and qualified engineer represented Tonga at the 2016 Olympics and then the winter Olympics earlier this year.
Mr Taufatofua said he would promote three main things as ambassador.
"Education is the biggest thing. Number two is access to health and making sure that the kids grow up healthy and with access to good nutrition and that sort of thing. I'm a sportsman so nutrition is always a top thing on my agenda," Mr Taufatofua said.
"The third thing is making sure that the voices of the kids are heard. Rather than a lot of talking down to kids, it's about asking them how they want their future to be."