His agent, Russel Hicks, said it was a four-year deal worth $20 million, with $9 million in guarantees.
The loss doesn't come as a surprise, after Manning turned down a three-year offer from the Bears last season.
"Man, it was tough to leave Chicago because I had so many bonds up there with coaches and players, especially the players, they were great," Manning told ESPNChicago.com. "But deep down inside, I feel like I got what I deserved. I feel like Chicago made their decision and I had to do what was best for me.
"I really didn't know this offseason, because of all the stuff with the CBA and the lockout, if the Bears were going to try and bring me back. I was like, well maybe they can't talk to me because they can't due to the lockout. As the lockout ended, I assumed Chicago would at least make a fair effort to bring me back. I mean, you kind of want to play out your career with the first team you played with, the first team that drafted you. But it didn't happen."
The departure leaves the Bears with little proven depth behind veteran Chris Harris and rising second-year player Major Wright. Craig Steltz is the only proven backup, but the club drafted third-rounder Chris Conte as a potential reserve, in addition to adding undrafted rookies.
Had the sides been able to come to an agreement for a Manning return, the safety had already been told he'd be involved in a three-player rotation, somewhat similar to last year's, which still featured Harris and Manning taking the majority of the snaps.
So Manning chose to sign with the Texans after receiving interest from several suitors, including the 49ers, Browns, Saints and Jets.
"I feel like those [Texans] coaches genuinely care about you and are putting together guys that want to win," Manning said. "They told me they envision me roaming the field on defense. It's a different scheme than I played in with the Bears, it's a 3-4 obviously, but it's a great opportunity. I talked with head coach Gary Kubiak, defensive coordinator Wade Phillips and secondary coach Vance Joseph, they all sound like great guys and they told me how they want me to play. I told them I want to learn to play Houston Texans football.
"They told me just free safety right now, but anything can happen. As you know, in my past, things have a tendency to change for me on defense."
A fifth-year veteran, Manning made arguably the most significant impact of his tenure with the team in 2011, when he contributed 85 tackles, an interception and five pass breakups. The performance came as somewhat of a breakthrough for Manning, who played virtually every spot in the secondary, before the team finally settled on him at strong safety.
During a season in which the Bears allowed the second-fewest touchdown passes (14), and gave up multiple touchdowns just twice (best in the league), Manning was one of five safeties in the NFL who played 75 percent or more of their defensive snaps to not give up a touchdown.
Manning also missed just three tackles, second-fewest among other NFL safeties who played 75 percent or more of their team's defensive snaps.
Manning contributed considerably on special teams as a return man as well, which is likely a role he'll take on with his new club. Since 2008, Manning leads the NFL in kickoff returns of 40 or more yards.
"To be honest, we only spoke about returning kickoffs briefly," he said. "I didn't talk to the special teams coach at all. I think they have excellent return men already in place in Houston. At this point, I was just happy to be part of the Texans organization. I'm totally on-board, and now I'm going to do my absolute best to try and help this team win some games and make the playoffs."
Despite Manning's resume, the Bears placed their hopes on the inexperienced Wright, even though late last season they tried to re-sign Manning to a contract averaging $2 million per year for three years.
Sources within the organization said the Bears wouldn't increase that offer, leaving Manning to shop his services elsewhere.
Michael C. Wright covers the Bears for ESPNChicago.com and ESPN 1000. ESPNChicago.com's Jeff Dickerson contributed to this story.