The deal, announced Thursday by the Nationals, includes a team option for 2021. The Detroit Free Press reported the deal is worth $19 million.
Sanchez, 34, will add depth to Washington's new-look rotation after boosting his appeal with a comeback season for NL East rival Atlanta. The Nationals signed Patrick Corbin to a six-year deal earlier this month.
Sanchez, a native of Maracay, Venezuela, was perhaps the Braves' most consistent starter as he posted a 2.83 ERA in 25 games, including 24 starts. He was 7-6 and had 135 strikeouts in 136 2/3 innings. It was a remarkable turnaround after Sanchez struggled in 2017 with a 6.41 ERA with Detroit.
Information from The Associated Press was used in this report.