Juan Agosto was originally signed by the Boston Red Sox as an amateur free agent in and released in . On January 18, he was signed by the Chicago White Sox. He debuted with the White Sox on September 7, 1981, a loss to the Seattle Mariners. Agosto entered the game in the top of the 2nd inning, relieving Richard Dotson after Dotson gave up five runs in the inning. He was with the White Sox when they won the American League West, and briefly pitched for them in the ALCS.