His doctoral thesis, Los Autos Sacramentales de Calderón, earned him various awards.

[2] His fundamental work is his History of Spanish Literature (Historia de la literatura española), published for the first time in 1937.

Thus, this work made Valbuena Prat one of the most prestigious literary historians of the postwar period.

[6] In addition to this work, Valbuena Prat published numerous studies on Spanish literature throughout his career, among which Algunos aspectos de la moderna poesía canaria (1926), Calderón: su personalidad, su arte dramático, su estilo y sus obras (1941), Historia del teatro español (1956) and Estudios de literatura religiosa española: época medieval y edad de oro (1963), as well as multiple editions of autos sacramentales and comedies of Pedro Calderón de la Barca, who had been the subject of his doctoral thesis.

He also wrote novels, Teófilo (1926) and 2+4 (1927), and poetry books such as Dios sobre la muerte (1939).