He played college football for the Ohio State Buckeyes, earning consensus All-American honors in 2002.

He was selected by the San Diego Chargers in the fourth round of the 2003 NFL draft, also played for the San Francisco 49ers and Green Bay Packers of the NFL, and was a member of the Packers' Super Bowl XLV championship team that beat the Pittsburgh Steelers.

In his first game as a starter against Fresno State, Wilhelm intercepted a David Carr pass and ran it 25 yards for a touchdown.

[2] The following year, he earned the Randy Gradishar Award as the team's top linebacker and made all of the defensive calls.

As a senior in 2002, Wilhelm was recognized as a consensus first-team All-American,[3] and helped his team win a BCS National Championship with a team-leading 11 tackles in a 31–24 Fiesta Bowl victory over the Miami Hurricanes.

Wilhelm was signed by the Philadelphia Eagles on August 4, 2009, after starting middle linebacker Stewart Bradley suffered a season-ending knee injury.