He's been on the non-football illness list since June, when he came off the practice field experiencing blurry vision.
Hal and the Texans announced less than a month ago that his cancer was in remission. The team will now have 21 days to add him to the active roster or to leave him on the list and not have him play for the rest of the year following his return to practice.
"We activated the 21-day window on him, so he'll be able to practice with the team," Texans head coach Bill O'Brien said, according to Sarah Barshop of ESPN. "At any point in time over the 21-day window we can decide to activate him to the 53-man roster, so we'll see where he's at and go from there. That's great news for (Hal) and for us."
Hal chose to avoid chemotherapy treatment to help preserve his body with an aspiration to play this season. He then followed a plan that involved a drug administered via IV in order to treat lymphoma found in his armpit and abdomen.
O'Brien says Hal continued to attend all meetings and he's "stayed on top of the X's and O's," while also working in the weight room and on the field.
"I knew I was going to play (again)," Hal said. "I just didn't know when. That's why I never stopped coming. I never stopped coming to practice, I never stopped working out. I just had a feeling that I was going to play again."
Hal has recorded nine interceptions over 61 games since being chosen with 216th pick of the 2014 NFL Draft.
He signed a three-year, $15-million contract extension with the Texans in 2017.