[citation needed] In 1931, García-Valdecasas joined the parliamentary group known as Agrupación al Servicio de la República ("The Grouping at the Service of the Republic"), an organization of intellectuals created by José Ortega y Gasset to support Spanish Republican politicians.

The Falange Española was a fascist successor group that split from the Movimiento Español Sindicalista.

García-Valdecasas participated as a speaker at the founding ceremony of the Falange, which was held on 29 October 1933 at the Teatro de la Comedia in Madrid.

In November 1933, he ran as a candidate for the right-wing Bloque de Derechas coalition in Granada, but was replaced by Ramón Ruiz Alonso.

[citation needed] After the breakout of the Spanish Civil War, García-Valdecasas joined the Francoist side, and in 1938 he was appointed Undersecretary of Education by Francisco Franco.