Gonzalez is one of three finalists for the 2012 National League Cy Young Award, joining Mets knuckleballer R.A. Dickey and 2011 winner Clayton Kershaw of the Dodgers.
Harper is contending against Reds infielder Todd Frazier and D-backs lefty Wade Miley for the Jackie Robinson NL Rookie of the Year Award.
And for NL Manager of the Year honors, Johnson is a final candidate with Dusty Baker of the Reds and Giants skipper Bruce Bochy. All three are former winners.
MLB Network announced the candidates and also will reveal the winners next week, with Rookie of the Year awards being presented Monday, Manager of the Year awards Tuesday and the Cy Young winners Wednesday.
In his first year with Washington, Gonzalez led the Major Leagues with 21 victories, led the team in strikeouts with 206 and had a 2.89 ERA in 32 games.
Harper was voted the NL's most outstanding rookie -- and for good reason. He played all three outfield positions and hit a respectable .270 with 22 home runs and 59 RBIs. His best game arguably came on May 6 against the Phillies. Harper showed how to get revenge in a 9-3 loss.
With two outs in the first inning, Phillies left-hander Cole Hamels hit Harper with a pitch, then later acknowledged that was intentional. After getting drilled, Harper advanced to third on a single by Jayson Werth. Harper was then able to get some payback by stealing home while Hamels tried to pick off Werth at first base.
Harper became the second player in Nationals history to steal home and the first to do so on a straight steal. Ian Desmond stole home as part of a double steal on April 20, 2011, against the Cardinals.
Johnson guided the Nationals to a 98-64 record and their first NL East Division title.
Bill Ladson is a reporter for MLB.com and writes an MLBlog, All Nats All the time. Follow him on Twitter @WashingNats. This story was not subject to the approval of Major League Baseball or its clubs.