In the 1950s, he established himself as an award-winning playwright whose best known works include Eva sin Manzana (Eve Without the Apple) (1953), Nuestro fantasma (1956) (Our Ghost) and Café del Liceo (Cafe of the Opera).

The film, starring the popular Spanish actor José Luis López Vázquez, tells the story of a repressed provincial spinster who late in life discovers that she is really a man and moves to the city to explore his new sexual identity.

Nunca es tarde (1977) (Never too Late) recounts in parodied fashion the miraculous pregnancy of a woman in her eighties through her mystical identification with a young male neighbor who she claims is the child's spiritual father.

Armiñán most acclaimed film of this period is El Nido (The Nest) (1980) which depicts the tragic consequences of the infatuation of an aging widower (Héctor Alterio ) for an adolescent girl played by Ana Torrent.

Armiñán's filmography over the next fifteen year remained notably slender, largely due to his return to television and his highly successful scripting of several dramatic series.

One of the few films he made during this period, La Hora Bruja (The Witching Hour) (1985) is noteworthy for its strong dramatic performances by Francisco Rabal, Concha Velasco and Victoria Abril in an amorous narrative involving the activities of a lascivious traveling magician.

Al otro lado del Tunel (The Other Side of the Tunnel) (1994), presents a similar story of passion and old age, this time with the amorous pair constituted by Maribel Verdú and Fernando Rey.