Amenabar demonstrated his creativity early in life. As a child, he composed guitar music that was later played to accompany short stories he wrote. By age 10, he was studying piano, and was considering a career as a musician or an illustrator. On a lark, he enrolled in film studies at the University of Madrid and began making short films—ironically, he failed his courses. While still an undergraduate, he collaborated on a screenplay with Mateo Gil about a cinema student who discovers what appears to be a snuff film. The script caught the attention of veteran director Jose Luis Cuerda, who encouraged Amenabar to make the feature "Thesis" (a.k.a. “Tesis”, 1996). The resulting movie earned widespread acclaim in Spain, won several Goyas—the Spanish equivalent of the Oscar—and announced the arrival of a potent new voice in Spanish cinema.
With his follow-up feature, also co-written with Gil, "Open Your Eyes" (a.k.a. “Abre los Ojos”, 1997), Amenabar solidified his standing. Because the film—which was tinged with science fiction and fantasy—did not delve into Spanish history or examine the faults and failings of contemporary people, some rejected it. More open-minded audiences and critics, however, were rewarded with a strong narrative, solid production values and terrific lead performances from Penelope Cruz and Eduardo Noriega, who was a frequent collaborator with the director. "Open Your Eyes" centered on a playboy (Noriega) who survives a horrific car crash and finds himself caught in a world that may or may not be real. The film was praised at the 1998 Sundance Film Festival and caught the eye of actor-producer Tom Cruise, who secured the remake rights and later starred in Cameron Crowe’s version, "Vanilla Sky" (2001). Cruise also served as executive producer of Amenabar's English-language debut, "The Others", which featured Nicole Kidman in a bravura lead performance as a high-strung woman who inhabits a large mansion on the remote Isle of Jersey during WWII. “The Others” did extraordinary business at the box office, thus solidifying Amenabar’s place at the Hollywood table.
Before segueing to his American debut, Amenabar provided the lilting underscores for two 1999 films made by close collaborators. He penned the music for "Butterfly” (a.k.a. “La Lengua de las mariposas"), directed by Jose Luis Cuerda, and for "Nobody Knows Anything" (a.k.a. “Nadie conoce a nadie”), directed by friend and frequent collaborator, Mateo Gil. Amenabar returned to making films in Spain with “The Sea Inside” (2004), an emotional tale about the 30 year struggle of Spaniard Ramon Sampedro (Javier Bardem) to end his life with dignity. The film won several awards, including a Golden Globe and the Oscar for Best Foreign Language Film.