Arnold Mario Portocarrero (July 5, 1931 – June 21, 1986) was an American professional baseball player and right-handed pitcher who appeared in 166 games pitched in the major leagues over all or parts of seven seasons for the Philadelphia / Kansas City Athletics and Baltimore Orioles.

Born in New York City of Puerto Rican descent,[1] he was listed as 6 feet 3 inches (1.91 m) tall and 196 pounds (89 kg).

The team was sold to Arnold Johnson, a Chicago investor, and moved from Philadelphia to Kansas City.

But Portocarrero struggled with arm miseries during 1955, the A's first season in Kansas City, and spent part of 1956 back in the minors.

In his final appearance in the big leagues June 15, 1960, he allowed five runs in relief to the Cleveland Indians, although only two of them were earned.