In 1999, Belmonte joined the International Red Cross and Red Crescent as project manager for a global campaign raising HIV/AIDS awareness within the Red Cross movement. The project was commended by UNAIDS as an example of best organisational practice.[1]
In 2001, Belmonte joined UNICEF as the organisation's spokesperson at the Palais des Nations in Geneva, and later as UNICEF's Chief of Communications there. In 2005 she served as campaign manager in a worldwide campaign on children and AIDS, co-launched by UNICEF and UNAIDS. She later joined UNICEF's regional office in Latin America and the Caribbean, where she helped design public advocacy efforts for child focused development initiatives in 24 countries.[1]
Belmonte was then appointed to the position of deputy director of Communications at UNICEF's headquarters in New York, a position she held until July 2012 when she took up the leadership of UNICEF's country program in Malaysia.[1] In this role, she worked with the country's corporate sector and focused on digital citizenship, child online protection and how innovation can deliver improved results for children.[3] Since 2016 Belmonte has been the organisation's Deputy Regional Director for East Asia Pacific.[1][2]