Miller was born in Richlands, Virginia. He attended Honaker High School and lived in Swords Creek, Virginia. 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. He set several school records in passing and leading the team to its first state championship game his senior year, in which they lost to King William High School 25-15.
While attending high school, Heath 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. He was also a forward on the basketball team where he earned the All-District and All-Region honors.
Nicknamed "Big Money" for his ability to gain first downs and score touchdowns, Miller became a three-year starter at tight end for the Cavaliers. He scored touchdowns in each of his first five games at Virginia thereby setting a school season-record for tight ends, and led Atlantic Coast Conference (ACC) tight ends in receiving all three seasons of his college career. He was a first-team All-ACC selection in 2003 and 2004, and a unanimous first-team All-American in 2004. Miller became the first ACC player to win the John Mackey Award in 2004, which is presented annually to the top college tight end of the season.
In his freshman season, Heath set an ACC record for freshmen tight ends with 9 touchdown receptions in a season. He followed that up with a sophomore campaign that saw him set ACC tight end records for receptions (70) and yards (835) in a season. In his junior season, Heath was awarded the John Mackey Award and was only the second player in Virginia history to be a unanimous All American.
Heath concluded his career holding ACC records for most career receptions (144), yards (1,703) and touchdowns (20) by a tight end. In Virginia history, these totals place Heath second in receptions, seventh in yards, and fourth in touchdown receptions, regardless of position. He also shares the school record for most 100-yard games by a tight end (3), and he caught at least one pass in 32 of his final 33 games. He majored in sociology.
The Pittsburgh Steelers selected Miller in the first round, thirtieth pick overall, of the 2005 NFL Draft. He was the third tight end drafted by Pittsburgh on the first round in 15 years. In his rookie season with the Steelers, he finished with 39 receptions for 459 yards and 6 touchdowns. During a four-game stretch in his rookie season, he caught five touchdown passes and was considered a strong candidate for the Offensive Rookie of the Year award. Though he cooled off, he remained a solid contributor in the Steelers' 2005 Super Bowl run. Miller caught three passes for 61 yards and one touchdown in the Steelers' 21–18 upset over top-seeded Indianapolis Colts in the divisional playoff round.
In the Steelers opening game of the 2006 season, Miller caught 3 passes for 101 yards, including an 87-yard touchdown reception, the longest touchdown catch by a tight end in a regular season game since 1974. It was also the longest catch ever recorded in the Steelers home stadium, Heinz Field. Replays showed that he should have been marked out of bounds at about the one-yard line, but the play was not challenged by Miami Dolphins coach Nick Saban quickly enough. Miller finished the season with 34 catches for 393 yards and 5 touchdowns.
In the 2007 Season, Miller set new career highs for touchdowns (7), receptions (47), and receiving yards (566). He benefited from new offensive coordinator Bruce Arians' system of offense which called for 3 tight ends, giving Miller more chances to catch passes. 2007 was the breakout year that most experts expected him to have after being under-utilized in his first two seasons. In Super Bowl XLIII, Miller had five receptions for 57 yards to help Pittsburgh win the game. Miller won his second Super Bowl Ring. Because the Steelers do not emphasize tight ends in their passing game, he has not compiled exceptional receiving statistics. Miller is recognized for capitalizing on the opportunities that he gets, rarely dropping a pass.
On July 30, 2009, the Steelers signed Miller to a new six-year contract that binds him to the team through the 2014 season. The contract is worth $35.3 million, including a $12.5 million signing bonus.
In 2011, Heath became the Steelers' all-time leader in career receptions for a tight end, passing Elbie Nickel. In that same year, he moved into the top 5 on the Steelers' all-time receptions list, moved into the top 10 on the Steelers' all-time receiving yards list, and was named to USA Football's All Fundamentals Team. 
For the 2010-11 season, Miller was elected by his teammates to be the offensive captain.
On October 11, 2012 in a loss against the Tennessee Titans, Miller had 6 receptions for 67 yards moving him past Louis Lipps for third place on the steelers all time receptions list.
During a 13-10 loss to the Cincinnati Bengals in week 16, Miller tore his ACL and MCL, causing him to miss the rest of the season; that same week, he was also selected to the Pro Bowl. After the season, Miller was voted MVP of the team by his teammates for his contributions in the 2012 season.
On March 4, 2014, Miller's contract was reduced from $9.5 million to $6.1 million, opening up around $3.4 million in cap space for the Steelers. He is now under contract through 2016, and the 2 new years include a base salary of $4 million.
He is the son of Earl and Denise. He and his wife, Katie, were married during the 2007 offseason and they have three sons, Chase, Jake, and Cole. 
Miller is involved with a number of charities. For several years now, Heath has participated in the Salvation Army and WTAE TV's Annual Mini golf Classic as a host to raise money for the Salvation Army. Heath has also been involved in charities such as fashion shows  and high school fundraising basketball games. 
^"Golf With Steelers Past and Present and Support Needy Kids and Seniors -- The Salvation Army and WTAE TV's Project Bundle-Up Slates 15th Annual Heath Miller Minigolf Classic." PR Newswire [Pittsburgh] 8 May 2012: n. pag. Web. 3 Oct. 2012.