He played college football at Ohio State, and was selected by the Miami Dolphins in the fourth round of the 2009 NFL draft.

Hartline attended GlenOak High School in Plain Township, Ohio, where he both played football and ran track for four years.

He began his football career as a quarterback, but in the fourth game of his sophomore year, he switched positions to wide receiver.

[3] He graduated from Ohio State in June 2009 with a degree in communication, but elected to forgo his final season of eligibility to enter the 2009 NFL draft.

Despite struggling with injuries and illnesses during the off-season and training camp,[10] Hartline played in the 2012 season opener against the Houston Texans and became the team's number one receiver with Brandon Marshall's trade.

[18] In 2020, Hartline was named to the AFCA "35 Under 35" Leadership Institute which annually recognizes the future leaders in the football coaching profession.

[20] On January 9, 2021, Hartline was promoted to passing game coordinator, on top of his title as wide receivers coach.

He is lauded for his multiple National Football League draft first round picks such as Garrett Wilson, Jaxon Smith-Njigba, Chris Olave and Marvin Harrison Jr.[23] Hartline's younger brother, Mike Hartline, is a former quarterback for the Indianapolis Colts and New England Patriots, and is currently the passing game coordinator and wide receivers coach for the Charlotte 49ers of the American Athletic Conference.