New England Patriots
Meriweather was selected in the first round (24th overall) of the 2007 NFL Draft by the New England Patriots. During his rookie season most of his time was spent on special teams, and he finished the season with 28 tackles. He played in Super Bowl XLII as a third safety in the Patriots' defense behind Rodney Harrison and James Sanders. During his second season in 2008, Meriweather recorded his first career interception in Week 2 off New York Jets quarterback Brett Favre. After starting strong safety Rodney Harrison suffered a season-ending injury against the Denver Broncos in Week 7, Meriweather started the final 11 games. In Week 14, Meriweather recorded his first career sack to stifle a late-game Seattle Seahawks drive and secure a Patriots victory. He finished the season with 83 tackles, two sacks, and four interceptions.
In Week 7, Meriweather had two interceptions against the Tampa Bay Buccaneers, including one returned 39 yards for a touchdown, and was named AFC Defensive Player of the Week. He started all 16 games and finished the 2009 season with 83 tackles and five interceptions, and was named to his first Pro Bowl as a replacement to the injured Jairus Byrd.
Brandon Meriweather was not part of the Patriots base defense to begin the 2010 season, something which Meriweather described as a coaching decision as a result of him freelancing in the defense during training camp. After being replaced as a starter in Weeks 2 and 3 by James Sanders, Meriweather returned to his starting role in Week 4.
In Week 6, Meriweather was penalized for a helmet-to-helmet hit on Baltimore Ravens tight end Todd Heap. While Heap walked off the field and would later return, the hit, grouped together with other helmet-to-helmet hits on defenseless receivers from NFL players during the week, sparked controversy over the protection of players. The NFL took action the following Tuesday when they fined Meriweather $50,000 for the hit. Following the game, the league announced that it would begin suspending players for dangerous hits, particularly those involving helmet to helmet hits on defenseless receivers.
In 16 games played (13 starts), Meriweather recorded 68 tackles, three interceptions, and six passes defensed. He was named to his second Pro Bowl following the season.