Miller played college football for the Virginia Cavaliers, earning unanimous All-American honors and winning the John Mackey Award.

[2] He played quarterback for the Honaker Tigers high school football team, where he earned the Associated Press Player of the Year honor as a senior and was a two-time AP All-State selection.

He also earned the All-Southwest Virginia first-team honors at quarterback and was a second-team all-state selection at defensive back, adding Region D Offensive Player of the Year accolades.

[2][4] While attending high school, Miller also played first base for the baseball team where he earned the Black Diamond District first-team honors, and was an All-Region and All-State selection.

Originally signed to play quarterback, Miller made the transition to the tight end position during his redshirt freshman year.

He also threw one pass during his college career, connecting with fellow tight end Patrick Estes for a touchdown against South Carolina in 2002.

In a comeback win against Wake Forest, he led the team in catches for the fourth consecutive game with 7 receptions, 94 receiving yards, and 1 touchdown.

[11][12] He entered training camp competing with veterans Jerame Tuman and Matt Kranchick for the starting tight end position.

He made his professional regular season debut in the Pittsburgh Steelers' season-opener against the Tennessee Titans and caught his first career touchdown on a three-yard pass from Ben Roethlisberger in a 34–7 victory.

On January 8, 2006, he appeared in his first career postseason game and caught two passes for 15-yards in a 31–17 AFC Wildcard victory over the Cincinnati Bengals.

The following game, Miller caught three passes for 61 yards and one touchdown in the Steelers' 21–18 upset over the top-seeded Indianapolis Colts in the divisional playoff round.

Miller started the season-opener against the Miami Dolphins and caught three passes for 101 receiving yards and scored an 87-yard touchdown reception in a 28–17 victory.

[13] He was named the starting tight end by Mike Tomlin after beating out Jerame Tuman, Matt Spaeth, and Jonathan Dekker.

In a Week 10 matchup against the Cleveland Browns, Miller caught five passes for a season-high 71 receiving yards and a touchdown in a 31–28 victory.

On January 5, 2008, the Pittsburgh Steelers faced the Jacksonville Jaguars in the AFC Wildcard game and Miller caught eight passes for 85-yards and scored on a 14-yard touchdown reception in a 31–29 loss.

Miller began the season making three receptions for 26 yards in the Pittsburgh Steelers' 38–17 season-opening victory over the Houston Texans.

On October 5, 2008, he made five receptions for 45 receiving yards and caught his first touchdown of the season on a one-yard pass from Ben Roethlisberger, in a 26–22 win over the Jacksonville Jaguars.

On January 15, 2011, the Pittsburgh Steelers faced the Baltimore Ravens in the AFC Divisional round after having a bye during the wildcard.

On February 6, 2011, the Pittsburgh Steelers appeared in Super Bowl against the Green Bay Packers, with Miller catching two passes for 12 yards during the 31–25 loss.

During a Week 7 matchup against the Arizona Cardinals, Miller made four receptions for 59 yards and a touchdown, while also having his first career carry for a six-yard gain in a 38–20 victory.

On December 19, 2011, the Pittsburgh Steelers played the San Francisco 49ers and Miller finished the 20–3 loss with five receptions for a season-high 82 receiving yards.

[13] New offensive coordinator Todd Haley named him the starting tight end to begin the regular season, over Jamie McCoy, Leonard Pope, and David Paulson.

On September 23, 2012, Miller caught a season-high eight passes for 60 yards and tied his career-high with two touchdown receptions in a 34–31 loss to the Oakland Raiders.

Prior to the beginning of the regular season, the Pittsburgh Steelers removed Miller from the Physically Unable to Perform list in hopes of him returning within a month.

With Matt Spaeth also recovering from a lisfranc surgery, the Steelers began the season with David Paulson and Jamie McCoy.

On October 20, 2013, Miller made two receptions for 17 yards and caught an 8-yard pass from Ben Roethlisberger for his only touchdown of the season during a 19–16 win over the Baltimore Ravens.

During Week 8, he made seven receptions for a season-high 112 yards and caught an 11-yard touchdown pass from Ben Roethlisberger, as the Steelers routed the Indianapolis Colts, 51–34.

[37] During a Week 14 contest against the Cincinnati Bengals, he caught a season-high ten passes for 60 yards and had his second career carry for a two-yard gain in a 33–20 victory.

[13] On January 3, 2016, he made three catches for 18 yards and caught his last career touchdown on a two-yard pass from Ben Roethlisberger during the Steeler's 28–12 victory.

[41] On January 17, 2016, Miller played in his last career game and caught one pass for a seven-yard gain during the Steelers' 23–16 AFC Divisional round loss to eventual Super Bowl 50 Champions the Denver Broncos.