"We're watching Gavin very closely and he'll certainly come into the mix in our Rugby World Cup preparation," said
Howley. "We want to give him an opportunity because he's spent a long time out."
The 2005 Lion returned from a 18-month sabbatical from rugby by signing for Saracens in October. He made his debut in December but lasted only four matches before suffering a calf injury.
That opened the door to a surprise move to the French big-spenders and he certainly caught the eye of Warren Gatland with an accomplished performance for Toulon in their 38-10 victory over Stade Francais at Stade Felix-Mayol.
Henson's stunning break set-up a try for Gabirieli Lovobalavu and he capped his dream debut with a second-half try of his own.
"I watched him play on Saturday against Stade Francais," added Howley, a Lion in 1997 and 2001.
"He played particularly well. He looks very fit. We all know Gavin's strengths, he's a very accomplished player, very skilful and he's very confident in his own rugby ability.
"His ability to play 12 or 13, with a kick, run, pass option, he is a very confident rugby player. His game-time is going to be monitored between now and the end of the season."
The two-time Grand Slam winner could make his Welsh comeback in the clash with the Barbarians on June 4, as he targets a first ever World Cup.
"While there is an intensity in the Top 14, international rugby has another intensity on top," added Howley.
"But having watched him on Saturday, he looks fit, he looks very enthusiastic, his work-rate off the ball was good, which was a very pleasing aspect of his game."