Januzaj, 19, impressed in United's 3-1 win over Hull at Old Trafford on Tuesday, days after being told he would be in Belgium's preliminary squad for the 2014 FIFA World Cup.
Bruce, a former United player who said the club would 'always be the greatest and best', believes Januzaj has a bright future ahead of him.
"We see the young players they've got today, Januzaj in particular, that kid's going to be a superstar isn't he?" Bruce told a news conference.
"If he keeps his feet on the ground, which I'm sure they will do here, then he's got everything the boy."
It came on a day when debutant James Wilson, 18, netted a brace in United's win, which was completed by Robin van Persie's late strike.
Bruce's side are winless in their past four Premier League matches, and the 53-year-old said keeping his squad focused had become a problem with their top-flight status secured.
Hull have a shot at their first major trophy when they meet Arsenal in the FA Cup final on May 17.
“Since we've got through (the FA Cup semi-final) the biggest problem I've had is keeping everybody focused on the job," Bruce said.
"After Swansea (in the league) it was over and done, and my hardest problem has been to keep everyone focused on what lies ahead and that's been very, very difficult.
"We need the final to come along quickly, but make no mistake, we'll be ready for it."
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