Later in 1960, Cimino signed a professional baseball contract with the Washington Senators. He started his career that season as a pitcher for the Class D Wytheville Senators and went 6–2 with a 3.43 earned run average. The next season, he moved up to the Class B Wilson Tobs, of the Carolina League. Cimino didn't have much success in 1961, going just 4–5 with a 5.61 ERA. However, he bounced back in 1962. On April 30, 1962, he tied a Carolina League record by striking out 20 batters in one game. He went 12–13 that season and lowered his ERA to 3.36, while using his "blazing fastball" to record 190 strikeouts in 190 innings.