The seven-time Pro Bowl receiver arrived at the Texans' facility to learn the team's new offense on Monday, sources told ESPN.com.
It's unclear whether Johnson will report to training camp with the other veterans on Friday, but his appearance at the facility was a positive development.
Rookies and injured players were required to report on Monday. The first practice of training camp will be Saturday at 8:30 a.m.
Johnson skipped organized team activities and a minicamp, both of which were voluntary, and missed the Texans' mandatory minicamp in June. He was frustrated at the prospect of entering what he thought might be another rebuilding season for the Texans.
He is the longest-tenured player on the team, having been drafted third overall in 2003. In May, Johnson made his frustrations public, saying he wasn't sure he still wanted to be part of the Texans organization.
Despite his absence, Johnson remained in contact with first-year Texans coach Bill O'Brien, whose public comments about Johnson have been consistently positive. O'Brien said he had no concerns about Johnson being able to pick up the team's offense when he did arrive.