[11] After studying performing arts in Seville, Juan Diego moved to Madrid in order to develop his acting career, featuring in Televisión Española shows (most notably in plenty of Estudio 1 plays),[12] likewise making his film debut in Eloy de la Iglesia's Fantasía... 3 (1966).

[14] Diego starred as Marcos, a popular television host and member of a post-Francoist party (and scorned husband), alongside Ana Belén and a big black dog in a love triangle in the 1977 zoophilia-themed film La criatura.

[16][17] He landed a breakthrough role with his performance in Mario Camus' 1984 film The Holy Innocents,[10] playing Señorito Iván, a repulsive authoritarian landlord from an Extremaduran cortijo, obsessed with game hunting and disdainful of his workers.

[26] Juan Diego appeared in Luis García Berlanga's last full-length film París-Tombuctú (1999), playing the anarchic nudist Boronat, a role that won him his second Goya Award for Best Supporting Actor.

[31][32][33] Another of his collaborations with Carlos Saura, his supporting performance in the 2004 film The 7th Day portraying Antonio Izquierdo (an illiterate man and co-perpetrator of the Puerto Hurraco massacre),[34] earned him Goya award nominations in consecutive years.

[9] Many fellow actors and friends attended his lying in repose at the Teatro Español, including Marisa Paredes, Ana Belén, Víctor Manuel, Imanol Arias, Gabino Diego, Eduard Fernández, Manolo Solo, Emilio Gutiérrez Caba, Carmelo Gómez, Mariano Barroso, and María José Goyanes.