The French defender collided with Hamilton forward Marios Ogkmpoe late in the second half as Celtic tried to hold onto their narrow lead over the home side. Jullien was treated by the Celtic medical staff and after a delay of a few minutes was able to carry on. He helped see out a clean sheet as the league leaders made it five wins from five in the Premiership.
Kristoffer Ajer also appeared to suffer a knock but speaking after the match Lennon was positive about their condition.
He said: "They’re fine. Chris Jullien had a wee minute - a second or so - of a blackout, but he was able to finish the game out.
"He was outstanding again today, defensively we looked solid."
Celtic's next fixture is away to Rennes in the group stages of the Europa League.