Left-handed pitcher Wade Miley was introduced at Minute Maid Park on Friday.
The Astros agreed to a $4.5 million, one-year contract with the 32-year-old, who hails from Louisiana.
Astros general manager Jeff Luhnow said the organization has been pursing Miley for a few years.
Luhnow also said Miley will be part of the starting rotation.
During his introduction, Miley was asked why he had his eyes set on Houston.
"It's close to home. (They) did a great job putting a championship team together here year in and year out, so just looking forward to trying to be a part of that and see what happens," Miley told reporters.
"His personality is the same. Pretty easy to know and easy to like, what you see is what you get with him. I think his approach to the game... he's always been super competitive, and when you play against him, you see that he's a fast worker. He's hard on himself. He's always been hard on himself because he expects a lot," Astros manager A.J. Hinch added.
FULL VIDEO: Houston Astros GM Jeff Luhnow and manager A.J. Hinch introduce new pitcher Wade Miley
Miley could earn an additional $500,000 in performance bonuses.
Justin Verlander and Gerrit Cole head a rotation also projected to include Collin McHugh and possibly Brad Peacock.
Dallas Keuchel became a free agent after the World Series and remains unsigned.
Miley was 5-2 with a 2.57 ERA in 16 starts and 80 2/3 innings for the Milwaukee Brewers last year.
He agreed to a minor league contract in mid-February, made three starts at Double-A Biloxi, then joined the Brewers in early May. He went on the disabled list with a strained oblique after just two starts and did not return to the Brewers until July 12.
Miley had a 1.23 ERA in four postseason starts - in Game 5 of the NL Championship Series, he walked leadoff batter Cody Bellinger, then was replaced by right-hander Brandon Woodruff in an unusual strategy employed by Brewers manager Craig Counsell.
Miley earned $2,743,011 last year, which included a prorated share of his $2.5 million salary and $700,000 in performance bonuses based on innings and starts.
An eight-year major league veteran who was an All-Star in 2012, Miley is 71-76 with a 4.26 ERA. He also has pitched for Arizona (2011-14), Boston (2015), Seattle (2016) and Baltimore (2016-17).
Welcome to Houston, Wade!
Astros sign All-Star outfielder Michael Brantley from Cleveland
Forrest Whitley among 11 non-roster pitchers invited to Astros spring training
Jake Marisnick and 6 pitchers reach 1-year deals to stay with Houston Astros
Houston Astros release spring training schedule
The Associated Press contributed to this report.