As a high schooler at Bellarmine Prep in Tacoma, Brie Felnagle earned accolades and awards to make her one of the most successful distance runners in Washington state high school history. During her prep career, Felnagle won two individual state cross country titles, six individual state track titles, and was named the 2004 Gatorade Track and Field Athlete of the Year. Felnagle finished her high school career with a second-place finish in the mile at the 2005 National Scholastic Championships before leaving Washington for the University of North Carolina.
Felnagle's impact at North Carolina was immediately felt. As a true freshamn, Felnagle was the Tar Heels' top finisher at the 2005 NCAA Cross Country Championships. Later that winter, Felnagle finished second in the 800m at the ACC Indoor Championships and was a member of the Tar Heels' national championship DMR squad.
As a sophomore, Felnagle's success was even greater. Felnagle earned All-American honors with her 22nd place finish at the NCAA Cross Country Championships, a feat she repeated at the NCAA Indoor Championships with her fifth place finish in the 3000m, before anchoring the Tar Heels to a victory in the DMR. During the outdoor season, Felnagle won the ACC Championships in the 800m and 1500m, before capping off her stellar season with a victory in the 1500m at the NCAA Outdoor Championships.
In 2008, Felnagle broke North Carolina's school record in the 1500m, and later competed in the US Olympic Trials. That Fall, Felnagle finished an impressive fourth at the NCAA Cross Country Championships.