Later that year he became the placekicker for the New Orleans Saints, for whom he set an NFL record (now surpassed) for most consecutive successful field goals to start a career, and then became the first kicker in NFL history to convert three field goals of more than 40 yards in the Super Bowl.

[10] Hartley's .950 field goal percentage was among the highest during the season[11] and earned him a nomination for the Lou Groza Award which goes to the nation's best placekicker.

[14] Hartley was signed by the New Orleans Saints on October 29, 2008, to replace Taylor Mehlhaff, who was released.

[19] On January 24, 2010, he made a 40-yard field goal in overtime against the Minnesota Vikings in the NFC Championship to send the New Orleans Saints to their first Super Bowl.

[20][21] He continued in Super Bowl XLIV, going 3-for-3 with field goals of 46, 44, and 47 yards in the 31–17 victory over the Indianapolis Colts.

He missed two field goal attempts in the Saints' Week 1 home win over the Minnesota Vikings.

[24] He later made three field goals despite windy conditions in a Week 2 win on the road against the San Francisco 49ers.

[32] While with the Saints, he was teammates with long snapper Justin Drescher and holder Chase Daniel, all of whom went to Carroll Senior High School.

[36] On December 13, 2014, Hartley was signed by the Cleveland Browns to replace Billy Cundiff, who had injured his knee.

[39] On August 11, 2015, Hartley was signed by the Pittsburgh Steelers to replace Shaun Suisham, who had torn his ACL.

[44] He was waived on January 28 after failing to receive medical clearance, as he has an artificial disk in his neck and not a fusion.

[45][46][47] On September 3, 2021, it was announced that Hartley signed with the Massachusetts Pirates of the Indoor Football League two days before their playoff semifinal game against the Frisco Fighters.