Tony Garcés, 18, has been missing since Monday morning when he was last seen waiting for a bus to head to Cal State Los Angeles.
Family members dropped him off at the corner of Bundy Drive and Pico Boulevard. He was wearing black pants, a gray polo shirt and carrying an American flag backpack.
Family members say it's unusual for the Santa Monica High grad to stay away from home without notice.
Anyone with information is being asked to contact Santa Monica Police Detective Leslie Trapnell at (310) 458-2256, or the missing teen's mother, Griselda de la Torre-Garcés, at (310) 867-0553.