Mantilla played in New York from the 1950s, inspired by Afro-Cuban jazz. He played with a number of latin jazz ensembles in the 1950s, including the La Playa Sextet, Xavier Cugat, Lou Perez, René Touzet, Miguelito Valdez, and Monguito Conjunto. He played behind Eartha Kitt in 1955. In 1960 he toured with Herbie Mann and recorded with Max Roach. He recorded with Al Cohn in 1961, and recorded with Freddie Hubbard, Buddy Rich, and Larry Coryell in the 1960s. From 1963 to 1969 Mantilla led his own band in Puerto Rico, and in 1970 joined forces with Max Roach's percussion ensemble, M'Boom.
Mantilla was a member of Art Blakey's Jazz Messengers in the 1970s, during which time the ensemble toured the U.S., Europe, and Japan. Following this he recorded with Gato Barbieri, Joe Farrell (1974), Richie Cole, Don Pullen (1976–77), Charles Mingus (1977–78), Walter Bishop, Jr., and Morgana King (1979). He toured Cuba with Dizzy Gillespie in 1977.