Johnson on Monday tweeted a photo of himself in a Cardinals helmet that included the hashtag #ImBack. A Cardinals media relations member then tweeted that Johnson had arrived at camp, which opened to injured players Monday and begins for the full team Friday.
"The Cardinals want me to play for them for a long time, and I want to be here for a long time," Johnson told the team's website. "So definitely things are going in a positive way."
The fourth-year running back had skipped a June minicamp and two organized team activity practices as he sought a contract extension. Johnson is heading into the final year of his rookie contract and is due to make $1.905 million in 2018.
He said he ultimately decided against holding out from camp after discussing his options with his representatives.
"I'm here to play football," Johnson said. "I trust my agency, Sportstars, and I know they'll get it done when the time comes."
Johnson missed the majority of the 2017 season after fracturing his left wrist during Week 1.
He has said that he is targeting 1,000 receiving yards and 1,000 rushing yards in his comeback season. The only players in NFL history to log both those marks in a single season are Roger Craig in 1985 and Hall of Famer Marshall Faulk in 1999.
ESPN's Josh Weinfuss and ESPN Stats & Information contributed to this report.