Julio Cesar Mateo (born August 2, 1977) is a Dominican professional baseball pitcher.

Mateo split the 2002 season between the Double-A San Antonio Missions, the Triple-A Tacoma Rainiers, and the Major League Mariners.

On August 28, Mateo broke his fourth metacarpal (ring finger) on his left hand while lifting weights.,[1] and missed the remainder of the '06 season.

On July 31, 2007, Mateo was traded to the Philadelphia Phillies for minor league shortstop Jesus Merchan.

He went 4–1 with a 1.43 ERA 15 saves in 35 relief outings for both the Double-A Reading Phillies and the Rainiers in the Mariners' organization.

He left spring training in 2006, after learning his older brother, Luis, had died in an automobile accident in the Dominican Republic.

[2][3] Mateo was optioned to Triple-A Tacoma immediately after the event and faced a 10-day non-pay suspension as well as a fine for not showing up to the ballpark for the game that night against the New York Yankees.

[4] While pitching in San Francisco's farm system, Mateo was arrested on July 27, 2008, in Albuquerque, New Mexico.

A police report says that as officers patted Mateo down in a hotel hallway early Sunday, he made a statement in Spanish denying the charges.