Hasselbeck was redshirted his first season and only took four snaps at quarterback as a redshirt freshman in 1997. However, he did play on all of the special teams units and registered two tackles. As a redshirt sophomore in 1998, Hasselbeck appeared in six games while spending most of the season as the backup to Scott Mutryn and completed nine of 12 passes for 140 yards and two touchdowns.

Hasselbeck earned the starting quarterback spot in preseason as a redshirt junior and played in all 12 games. During the season, he completed 145 of 260 passes for 1,940 yards and 11 touchdowns and also rushed for 198 yards and three touchdowns. In a 24–23 upset win against Syracuse, he was six for 13 in passing for 161 yards and had 11 rushes for 52 and one touchdown. He accounted for 213 of Boston College’s 269 yards and was named winner of the Orrie T. Scarminach Award, given to the Most Valuable Player of the Syracuse game. Hasselbeck was named the Big East Co-Offensive Player of the Week after Boston College’s 31–29 upset win over Notre Dame. During the game, he completed 20 of 30 passes for 272 yards, accounted for all four of the teams’ touchdowns (three pass, one rush), led the team in rushing with 60 yards, and accounted for 332 of Boston College’s 442 yards of offense. On November 26, 1999, he completed the longest touchdown pass in Boston College history, a 97-yarder to Dedrick Dewalt in a 38–14 loss against Virginia Tech. After the regular season, Hasselbeck played in the 1999 Insight.com Bowl against Colorado, to whom Boston College lost 62–28 During the game, he completed 13 of 32 passes for 146 yards and a touchdown and rushed for 25 yards.

Hasselbeck was originally signed by the Buffalo Bills as an undrafted free agent in 2000 and he was signed to the Philadelphia Eagles practice squad in 2002 as a free agent.

On July 6, 2002, he married television personality Elisabeth Filarski, whom he met in college. She was a Survivor contestant in 2001 and was a co-host on the ABC talk show The View from 2003 to July 2013. In September 2013, she joined Fox News, replacing Gretchen Carlson on the talk show Fox and Friends. The couple has one daughter, Grace Elisabeth (born April 2005), and two sons, Taylor Thomas (born November 2007) and Isaiah Timothy (born August 2009).

In 2003, he was signed by the Washington Redskins, for which he spent two seasons as a backup quarterback. He entered the starting lineup in 2003 when then-starter Patrick Ramsey was injured. On December 7, 2003, he completed 13 of 19 passes for 154 yards in leading the Redskins to a 20–7 win over the New York Giants. He threw two touchdown passes and no interceptions in that game. The following week, he had the lowest possible single-game passer rating (0.0) in a 27–0 loss to the Dallas Cowboys. Hasselbeck was 6-for-26 (23 percent) for 57 yards with four interceptions.

In May 2005, the New York Giants signed Hasselbeck to be their backup for quarterback Eli Manning. His only game action with the Giants consisted of two kneeldowns. On September 1, 2007, he was released by the Giants.

Hasselbeck was signed by the Arizona Cardinals on October 16, 2007, after having been a television color commentator for their game against the Baltimore Ravens just a few weeks earlier. He appeared in one game with the Cardinals. He was also previously on the rosters of the Baltimore Ravens and Carolina Panthers without participating in a game. Hasselbeck had a 63.6 career passer rating.

Hasselbeck was a participant in the first annual “Broadcast Boot Camp” June 18–21, 2007 at NFL Films in Mt. Laurel, New Jersey. He made his television debut on September 23, 2007, announcing the Arizona Cardinals-Baltimore Ravens game for NFL on Fox. He is currently a sports analyst for ESPN, and has been on SportsNet New York and Sirius NFL Radio for a trial period, as well. He also works as a fantasy football analyst and co-hosts Fantasy Football Now on ESPN2 and ESPN.com.