Merrill was the first player taken overall in the 2005 National Lacrosse League Draft by the Portland LumberJax, and in 2006 was named both the NLL's Rookie of the Year and Defensive Player of the Year. During the 2009 NLL season, he was named a starter to the All-Star Game. When the LumberJax left Portland at the end of the 2009 season, the league held a dispersal draft. Merrill was selected with the first overall pick in the draft by the Edmonton Rush. On August 9, 2011, he was traded to the Philadelphia Wings, along with Rush forwards Dean Hill, Mike McLellan, and Edmonton's 41st selection in the 2011 entry draft, and the 4th round selection in 2013. In return, Philadelphia sent Athan Iannucci with teammates Alex Turner and Brodie McDonald, along with Philadelphia's first round draft picks in 2012, 2013 and 2014. On November 29th, 2018, Brodie was signed by the San Diego Seals where he was named captain.
In 2019, Merrill joined Paul Rabil’s new Premier Lacrosse League as a member of the Chaos Lacrosse Club.
Canadian Box career
Junior
Merrill played his junior lacrosse with the Orangeville Northmen of the OLA Junior A Lacrosse League. In 2000, Merrill lead the Northmen to a league championship. In 2001, Merrill was awarded the "John McCauley Award" for Best Defensive Player, and shared the "B.W. Evans Award" for Top Graduating Player with Dan Bowman the following year.
In 2006, he helped the Canadian national lacrosse team to an historic win at the World Lacrosse Championship in London, Ontario. He had an outstanding tournament, being named Best Defender and earning All-World honours.
Personal
Brodie and his brother Patrick were a member of the Toronto Rock. Both Brodie and Patrick are members of the Brampton Excelsiors in the Major Series Lacrosse and both were members the Hamilton Nationals of Major League Lacrosse. He was named by Inside Lacrosse as "The Best Player in the World."-Inside Lacrosse. He is also the Dean of Students and head men's lacrosse coach at The Hill Academy in Vaughan, Ontario. At a very young age, he was best friends with lacrosse player Kyle Miller. Both loved the game and chose to play together at the Salisbury School, a prep school in Connecticut, but went on to different colleges. Kyle and Brodie were reunited as teammates on the Canadian roster for the 2006 World Lacrosse Championships. Kyle was diagnosed in 2011 as having Osteosarcoma. He died on June 8, 2013. Brodie is the main editor for the online lacrosse magazine, Brodie Merrill Lacrosse.