The person spoke on the condition of anonymity Monday because Gorzelanny needed to pass a physical, which is scheduled for Tuesday.
MLB.com, citing two unidentified baseball sources, reported outfielder Michael Burgess, right-hander A.J. Morris and left-hander Graham Hicks would be sent to the Cubs as part of the trade.
A 28-year-old left-hander, Gorzelanny is 36-37 with a 4.68 ERA in six seasons. He was 7-9 with a 4.09 ERA in 29 games (23 starts) last year but became expendable after the Cubs acquired Matt Garza in a trade with Tampa Bay.
The Nationals also agreed to a $2.75 million, one-year contract with pitcher John Lannan and avoided salary arbitration. The 26-year-old lefty was 8-8 with a 4.65 ERA last season, when he made $458,000.