The veteran receiver signed a five-year deal Friday for nearly $31 million to remain with the Miami Dolphins, his agent said. The contract includes $12.5 million guaranteed.
"I'm happy; I think they're happy," Hartline said. "That's probably the good sign of a good deal."
Quarterback Matt Moore signed a two-year deal to remain as Ryan Tannehill's backup rather than test free agency and pursue a possible starting job.
Hartline, who also could have become an unrestricted free agent Tuesday, instead opted to remain with the team that drafted him in 2009.
"I believe he could have signed for more in the open market with another team, but he wanted to remain with the Dolphins for less money," agent Drew Rosenhaus wrote in a text message to The Associated Press.
Hartline tweeted a photo of himself signing the deal in the Dolphins' offices.
"Blessed to be a Dolphin for 5 more years," he tweeted. "Now it's time to win some championships."
Working with rookie Tannehill, Hartline led Miami last season with 74 receptions for 1,083 yards, both career highs, despite missing most of the preseason because of injuries. However, he caught only one touchdown pass and has career totals of six scores in 183 receptions.
While Hartline is a solid No. 2 target, landing a top receiver for Tannehill remains the Dolphins' foremost offseason priority, and they're expected
Hartline said he'd be happy to help upgrade the receiving group.
"As soon as I signed, I'm like, Look, let's go recruiting now. So I hope I'm invited to those dinners," he said.
Moore was beaten out for Miami's No. 1 job last summer by Tannehill and played in only two games off the bench. The five-year veteran started 12 games for the Dolphins in 2011 and had his best season, throwing for 2,497 yards and 16 touchdowns with nine interceptions, but said he's content with continuing as Tannehill's backup.
"Whether you're a starter or a backup in this league, it needs to be the best fit and the right team," Moore said. "To me there's no other team out there that's perfect. I think myself and the Miami Dolphins fit perfectly together."
Moore said remaining with the Dolphins appealed to him partly because he expects substantial improvement by a team that has endured four consecutive losing seasons.
"This team is definitely going places," he said. "There are big things to come, and I didn't want to miss out."
General manager Jeff Ireland hopes to re-sign at least a couple of other players before they become free agents. Possibilities include tackle Jake Long, running back Reggie Bush, cornerback Sean Smith, safety Chris Clemons, tight end Anthony Fasano and reserve tackle Nate Garner.
"I am excited that we have been able to reach an agreement with both Brian and Matt to keep them as members of the Miami Dolphins," Ireland said in a statement.
"Brian is an ascending player that has steadily improved over his first four years with the organization. He has represented himself positively both on the field and throughout the South Florida community. Matt has been a valuable contributor to the Dolphins ever since he arrived two seasons ago."
This week's deals leave the Dolphins with enough salary cap room to sign at least one major free agent. On Monday, they designated defensive tackle Randy Starks as their franchise player.