MLB Network reported earlier Tuesday that Parra and the Rockies agreed to a three-year deal worth $27.5 million.
Parra did not reveal any specifics of the deal in his announcement, which was posted on his official Twitter account.
Parra, 28, is a two-time Gold Glove winner who can play all three outfield positions. He will join a crowded outfield in Colorado, which already has Carlos Gonzalez, Charlie Blackmon, Corey Dickerson, Ben Paulsen and Brandon Barnes.
Citing their surplus of outfielders, Fox Sports reported later Tuesday that the Rockies were engaged in trade talks with the Baltimore Orioles.
Parra split last season with the Orioles and the Milwaukee Brewers, batting .291 with a career-high 14 home runs, 51 RBIs and 14 stolen bases.
Parra has a career .277 average with 56 homers and 311 RBIs in seven seasons with the Orioles, Brewers and Arizona Diamondbacks.