Griffith proved themselves to be a real premiership contender after snapping Waratahs' 10-game winning streak.
The premiers hadn't lost since being surprised by Wagga City in round one, but struggled to make inroads against the Blacks at Exies Oval on Saturday.
Saione Ahomana did most of the damage, crossing for four tries in the 53-26 victory.
Coach Craig Morriss was thrilled with the number eight's performance and the team as a whole.
"We've been working pretty hard on discipline and there was limited penalties and our guys played very structured," Morriss said.
"We had two area of focus in the game - discipline and energy - and they bought both of those."
The Blacks lead 27-14 at the break, but it was the Waratahs who struck first in the second half to reduce the margin to eight points.
However Griffith had enough answers.
"It was a big test and the boys did very well," Morriss said.
"Tahs were down in numbers but we will take that and the boys worked hard to get it done."
Griffith have now won their last six games to move into third.
However with a clash against second-placed Ag College on the horizon, Morriss doesn't want the side to get too far ahead of themselves.
"I think we are up there with (the best) but we are only up there as long as we keep working hard," he said.
"We can't get carried away with ourselves but keeping improve our game and our discipline."