The 34-year-old, left-handed-hitting Pena gives the Astros a legitimate designed hitter as Houston moves to the powerful American League West Division in 2013.
"This was my most attractive option," said Pena, who hit 19 home runs with 61 RBIs and 87 walks for the Rays last season. "It re-energizes me. It's a new beginning, they're a young team. We have a new staff. We have new colors in the uniforms. Everything is so fresh, so I wanted to be part of that. When the Astros expressed interest, I immediately lit up. The pursuit on both ends -- I thought it was persistent. We wanted to make something happen. It was attractive to me immediately.
"I'm here to provide my services to be the best I can be. Not only with the bat and glove, I want to make sure I'm also a good teammate and to contribute to having good chemistry in the clubhouse. I'm just one more Astro."
It's a fresh start for Pena as well as the Astros, who named Bo Porter as their manager in September. The Astros unveiled new uniforms and a new color scheme in the fall.
Last season, the Astros scored only 583 runs and smacked 146 home runs.
"This one's big," general manager Jeff Luhnow said. "We needed to get a bat in the lineup that we felt confident and comfortable that was going to produce runs. He's going to make the whole lineup better, lot deeper."
The Astros reached an agreement with Pena's agent Scott Boras on Friday night. Terms of the deal were not disclosed.
"It was a good match," Luhnow said. I think Scott saw it right away and Carlos saw it right away. I think Scott saw that this would be a good opportunity for Carlos. He would have an opportunity to play every day here."
Luhnow said the signing of Pena does not mean the Astros' interest in free agent Lance Berkman has waned.
"We need to do everything we can to improve this team," Luhnow said. "And if we get to the point where Lance is interested in playing and find if we can utilize him, which we obviously can, and he's healthy, then we will have a conversation. He's someone we will continue to communicate with.
"We needed to do this signing [with Pena] for the sake of the Houston Astros for next year. There's still some work to be done."
Luhnow spoke with Berkman last week and again briefly on Monday. Berkman and Luhnow mutually decided to wait until mid-January to see where both parties are at. Luhnow said he feels Berkman is still capable of playing the outfield as well as first base.
Houston is coming off 106- and 107-loss seasons -- the club's two worst records since beginning play in 1962 as the Colt .45s. A young team in a rebuilding process, the Astros are in dire need of hitting, and Pena appears to be a good addition.
Over the past six seasons, Pena has averaged 32 home runs, 91 RBIs and 94 walks. In 2007, he had career highs in home runs (46), RBIs (121), walks (103), slugging percentage (.627) and OPS (1.037) while earning American League Comeback Player of the Year honors for Tampa Bay.
Pena has logged 30 or more home runs and 100-plus RBIs three times.
"I have so many years ahead of me," Pena said. "I feel I have so much to give."
And not just at the plate. Pena's leadership will be welcomed on a team that has very few players remaining who started the 2010 season with the big club.
"He's a veteran guy who will be able to encourage and help guys like [second baseman] Jose Altuve, yet at the same time encourage and help guys like [starting pitcher] Bud Norris," Luhnow said. "That's the type of veteran we want in the clubhouse."
Pena wouldn't say what other teams he was considering, but he feels Houston is the best place for him despite joining a franchise that has lost 213 games over the past two seasons.
"It was inviting to me," Pena said. "I've had experiences on teams [Tampa Bay] where we were thought to be the worst in baseball. Then very quickly we were in the World Series."
Luhnow and Pena wouldn't rule out the possibility of him playing first base at times instead of Brett Wallace.
"[Pena] provides flexibility, because he's a left-handed batter who can play a good first base defensively," Luhnow said. "That gives you options.
"There's a lot of good right-handers in our division and in our league that we're going to be facing. I can see certain days having Wallace play third and Pena play first. That way you get two left-handed bats in the lineup."
"I can play first base every single day," Pena said. "I can play defense. I'm here to do what my skipper wants."
A veteran of the AL, in addition to Tampa Bay, Pena has played for Texas, Oakland, Detroit and Boston as well as the Chicago Cubs.
Houston's large Hispanic population is a good market for Pena, who is bilingual and bicultural. He answered some questions in Spanish during Monday's news conference.
Addressing a need for a designated hitter on Monday, Luhnow said the club's focus now is to add another arm in the bullpen to replace Wilton Lopez, and to consider adding another outfielder.
Richard Dean is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.