Harris, 35, served as one of Astros manager A.J. Hinch's go-to relievers last season. According to ESPN, Harris is expected to jump into an eighth-inning role and could eventually get save opportunities with the Nationals in 2020.
Harris, a 2016 All-Star selection, posted a 1.50 ERA and notched 62 strikeouts in 60 innings for the Astros last season. He also recorded 26 holds and four saves as the Astros led MLB with 107 wins in the regular season.
During the postseason, Harris made 12 appearances and had a 0.93 ERA while striking out 11 in 9 2/3 innings. Despite his strong numbers in the playoffs, the right-hander struggled during key moments in the 2019 World Series.
In Game 7 against the Nationals, Harris allowed the go-ahead home run to Howie Kendrick. He also gave up a two-run homer to Anthony Rendon in the seventh inning of Game 6 that handed the Nationals a 5-2 lead.