"It's time for me to step aside to take on new professional and personal challenges," the 35-year-old outfielder wrote Monday on Instagram. "It's not an easy decision to make for any athlete, but I am happy with what I have achieved in these 12 years in the major leagues."
Parra said his new role with the Nationals "is undoubtedly a dream job to start a new chapter."
Parra became a fan favorite as he helped Washington win the 2019 World Series, making "Baby Shark" his walkup song. The Nationals released a video tribute to Parra, who signed a minor league contract with the team before this season but did not appear in any games.
He hit .237 with 90 homers and 532 RBI for Arizona (2009-14), Milwaukee (2014-15), Baltimore (2015), Colorado (2016-18), San Francisco (2019) and Washington (2019, 2021) and spent 2020 with the Yomiuri Giants in Japan's Central League.