The winning kick was set up when Laron Landry intercepted Aaron Rodgers at his own 39-yard line. The Packers' Charles Woodson was called for pass interference at Washington's 23, and one play later Gano drilled the game-winner for the Redskins (3-2).
Donovan McNabb went 26-of-49 through the air for 357 yards and a touchdown, finding Santana Moss for seven passes totaling 118 yards.
Rodgers finished the game 27-of-46 for 293 yards and a touchdown and Brandon Jackson gained a career-high 115 yards on 10 carries for the Packers (3-2).
Green Bay lost tight ends Jermichael Finley and Donald Lee, defensive lineman Ryan Pickett and linebacker Clay Matthews to injuries during the contest.