He is best known for his performance as Marcos Novoa Pazos in the Antena 3 series The Boarding School (Spanish: El internado) and for his role in The Blind Sunflowers (Los girasoles ciegos), which earned him a nomination for the Goya Award for Best New Actor.

[3] Rivas began his career as a child actor in 1998 with the TVG series Mareas vivas (English: Live Tides), made in the Galician language.

Rivas came to wider media attention in 2006, when he landed the role of Moisés in the LaSexta series SMS, opposite Yon González, Amaia Salamanca, Mario Casas, and others.

From 2007 to 2010, Rivas portrayed Marcos Novoa Pazos in the Antena 3 series El internado (The Boarding School), which brought him international popularity.

Rivas made his feature film debut in José Luis Cuerda's The Blind Sunflowers (2008),[4] opposite Javier Cámara and Maribel Verdú, which earned him a nomination for the Goya Award for Best New Actor.