The Watson trade was announced by the Pirates and Dodgers, who will send minor leaguers Oneil Cruz and Angel German to Pittsburgh in return.
Watson began the season?as the Pirates' closer but was removed in favor of Felipe Rivero after blowing consecutive save opportunities in Baltimore in June.
The 32-year-old Watson has a 5-3 record and 3.66 ERA in 47 appearances this season with 35 strikeouts and 14 walks. He will be a free agent after the season.
Cingrani, 28, has a 5.40 ERA over 25 appearances in 23? innings, but has allowed nine home runs.?
The Dodgers had only two left-handed relievers with more than 10 innings pitched this season prior to Monday's deadline deals.?
Cruz is hitting .240 and German has a 1.91 ERA for Class A Great Lakes.
ESPN Stats & Information and The Associated Press contributed to this report.