Martínez Sierra's literary career began at the age of 17 with the publication of El poema del trabajo ('The Poem of Work', 1898), a volume of poetry in the modernist style.

[citation needed][1] His major works include La sombra del padre ('Shadow of the Father', 1909), Primavera en otoño ('Spring in Autumn', 1911), Sólo para mujeres ('For Women Only', 1913), Mamá ('Mama', 1913) and El reino de Dios ('The Kingdom of God', 1916).

Canción de cuna ('Cradle Song', 1911), which has been called his "masterpiece",[citation needed][2] was popular across the Spanish-speaking world, and an English-language adaptation transferred to Broadway in 1927.

The deft handling of female characters in Martínez Sierra's works has been attributed to the collaboration of his wife, the writer María Lejárraga.

[6] Amongst a series of Spanish and foreign playwrights[7] whose work he produced "in a new, forward-looking style",[8] it was at Martínez Sierra's invitation that Federico García Lorca created and staged, at the Eslava, his first play, El maleficio de la mariposa ('The Curse of the Butterfly'), in 1920.