Aston Villa
On 22 January 2007, Carew signed for Aston Villa in an exchange deal with Lyon for Milan Baroš. Carew penned a three-and-a-half-year deal at the Birmingham-based club. Carew went on to receive the No. 10 jersey left vacant by Baroš' departure.
Carew made his debut in the 3–1 defeat to Newcastle United, but went on to score his first goal for the club in a 1–0 victory against West Ham United just three days later. Villa manager Martin O'Neill praised Carew's performance after the match.
Carew began the season as Villa's first-choice forward and much was expected of him by the Villa fans. However, despite some promising performances, it took Carew nearly two months to score his opener for the season against Everton in a 2–0 victory. He also suffered an injury in the same game and was out of action for six weeks with a hamstring problem. He scored on his second match back in the Villa side in a 3–0 away win against Middlesbrough in November. He then followed this up with a headed goal against Blackburn Rovers in a 4–0 victory as Aston Villa began to climb the Premiership table. December brought just one goal for Carew, a 30-yard run and shot against Manchester City, but he was instrumental in several of the goals Villa scored.
Carew scored two goals against Reading on 12 January and was unlucky not to be awarded Man of the Match which went to Martin Laursen. He scored his first hat-trick for seven years and his first ever for Aston Villa against Newcastle United on 9 February in a 4–1 win. Gareth Barry allowed him to do so by kindly relinquishing his usual penalty taking duties so Carew could score his third. On 12 April 2008, Carew scored for Aston Villa against Derby County at Pride Park in the Premier League, in the 26th minute and Villa went on to win the game 6–0. On 20 April 2008, Carew scored twice against Birmingham City in the Birmingham derby at Villa Park, which Villa went on to win 5–1. He continued his scoring run with a header the following week, in a crunch game at Everton's Goodison Park, which finished 2–2. It would be his 13th and final goal of the season, crowning him as Villa's top scorer for the 2007–08 season.
Carew scored his first goal of the 2008–09 campaign by scoring the first goal in Aston Villa's 2–2 draw over Odense in the Intertoto Cup. On 14 August 2008, Carew signed a 12-month extension to his contract, thus taking him through to 2011 with his current deal.
Carew scored the opening goal in Villa's 4–2 win over Manchester City at Villa Park. He then scored his second league goal against Stoke City as they went on to lose the match 3–2 when Mamady Sidibe scored a late winner. He quickly added his 3rd of the season in the 2–1 defeat of local rivals West Bromwich Albion; and with Gabriel Agbonlahor on the scoresheet again the pair began to form a formidable partnership. They both scored again and assisted each other's goals in a 4–0 victory in the Premier League at Wigan Athletic on 26 October 2008. Carew scored the winning goal in the UEFA Cup for Villa in a Group F match away to Slavia Prague on 6 November 2008, Villa midfielder Steve Sidwell struck the ball towards goal but it hit Carew and went in, therefore the goal was credited to Carew; it turned out to be the winning goal and continued Villa's 100% record in the competition's group stages and the 1–0 victory saw Villa go to the top of the group. Carew made the headlines in late October due to his personal behaviour. He was fined two weeks wages by Martin O'Neill for being in a pub near a Birmingham lap dancing club the night before Villa's UEFA cup group stage match with Ajax.
Soon after the controversy, Carew sustained a back injury that kept him out of the side for several months. During this time, Villa boss Martin O'Neill signed England international striker Emile Heskey to fill the gap left by Carew's absence. Heskey appeared to have taken Carew's place in the starting line-up for a number of weeks. However, his own injury woes and Carew's good form on return meant the Norwegian regained his place in the side. Carew played his first game after his injury on 31 January 2009 in a goalless draw with Wigan Athletic. In the last 32 of the UEFA Cup, Carew earned Villa a first leg draw with CSKA Moscow, after going 1–0 down to Vágner Love's goal. On 1 March 2009, Carew came off the bench to score a lob-shot volley in the 2–2 draw against Stoke City in the Premier League, which was later voted the team's goal of the season. He scored an equalising goal in the away fixture against Manchester United at Old Trafford before also netting the first goal in the home tie against Everton as Villa fought back from 2–0 and 3–1 down to draw 3–3. Further goals against Hull City and Middlesbrough took his league total to an impressive 11 goals from just 25 appearances.
Due to the persistence of fellow strikers Heskey and Agbonlahor, Carew initially struggled to hold down a regular spot in the starting eleven at the beginning of the 2009–10 campaign. Nevertheless, while being used as a substitute Carew still managed to score several important goals for Aston Villa. On 7 March 2010, manager Martin O'Neill chose to include Carew in the starting eleven in an FA Cup game against Reading. He took the opportunity characteristically and scored a hat-trick as Aston Villa came from two goals behind to defeat Reading 4–2 in the FA Cup quarter final. This made Carew the competition's top scoring striker, raising questions as to why the Norwegian was rarely included in Villa's starting eleven. Carew began to feature in the Villa team once more as the season progressed; goals against Wolverhampton Wanderers, Sunderland and Chelsea helped the Norwegian go neck and neck with Gabriel Agbonlahor as the club's joint top scorers for 2009–10.
Due to an injury to Gabriel Agbonlahor, Carew started the new campaign upfront with support from Ashley Young. However, due to both injury concerns of his own and a loss of form, his place in the team was taken by Emile Heskey limiting him to cameo appearances from the bench. As the season progressed, Carew's first team appearances became less frequent. Later that month, he allegedly missed a Villa game due to heavy snow disrupting his travel.
Carew spoke out about his limited chances under the new system under manager Gérard Houllier to a Norwegian TV station. Despite ongoing rumors in the press about a dispute between the former Lyon pair, Houllier revealed that Carew had been left out of the Aston Villa squad to work on his fitness. However, when Villa signed Darren Bent for £18 million, Carew's first team opportunities were further reduced.
On 27 May 2011, Aston Villa announced that Carew was one of a number of players released by the club after their contracts expired.