António Wagner Diniz was born in Lisbon and received a higher degree in singing at the National Conservatory, in the class of Joana Silva. With a scholarship from the Calouste Gulbenkian Foundation, he studied in Paris with Elizabeth Grümmer and at the Basel Academy of Music with Kurt Widmer, obtaining higher degrees in concert and opera singing. In Basel, he had the opportunity to work with Inge Bohrk, Reri Grist, Montserrat Figueras and René Jacobs, among others.

In addition to having performed with all Portuguese orchestras, he collaborated with the Swiss Radio Orchestra, the Basel Symphony, the Lithuanian National and the Malaysian National, under the direction of conductors such as Jost Meier, Moses Atzmon, Jaques Mercier, Michel Corboz, Adrian Stern, Hans Martin Linde, René Jacobs, Ketil Haugsand, Harry Christophers and Manuel Ivo Cruz, among others. 

As a recitalist, he has worked with José Bom de Sousa, Nuno Vieira de Almeida and João Paulo Santos, performing at the main Portuguese festivals and those in Locarno, Flanders, La Granja, Ischia and Macau. He collaborated in the opera seasons of the Teatro Nacional de São Carlos and sang in venues such as the Théâtre de la Monaie in Brussels, Philarmonie in Berlin and the Tokyo Opera City Hall in Japan.

He was a member of the groups Segréis de Lisboa, Real Theatro de Ópera de Queluz and the International Opera Company, with which he has performed in the East (India, Malaysia and Thailand).

He has been a singing teacher at the Escola de Música do Conservatório Nacional de Lisboa since 1987, and was its Director from 2000 to 2010. Since then he has directed the Orquestra Geração, a social project based on El Sistema that involves more than 1000 children and young people, for which he received the National Teachers Award from the Ministry of Education.