The wide receiver tweeted a picture of himself signing the deal earlier today.
The 26-year-old told NFL.com: "It feels great. It feels great to know hard work and perseverance is worth something. But now it's about winning games. I think we're on the right path. I think we're close.
"I'm excited to see what happens in free agency. We want to win. We're set up so we have cap room to make some moves, and that's one way we can win football games. It's important. And the draft will be important, too. It's exciting."
Hartline made over 1,000 receiving yards in 2012.