Juan Arango put the Foals in front in the 28th minute before sending in the ball which Adrian Ramos put into his own net to double their lead.
Raffael then added a third as Lucien Favre's side overpowered Berlin, probably ending any lingering hopes they had of playing in Europe next season.
With Wolfsburg, Augsburg and Mainz all dropping points earlier on Saturday, Gladbach sensed their chance to take a decisive step towards a place in Europe next season.
After only five minutes, they had the chance to go in front when Patrick Herrmann's cross was met by Max Kruse at the far post, but he shot into the side-netting with the goal gaping.
Hertha responded with a good chance of their own in the 20th minute when Ramos' cross picked out Anis Ben-Hatira, but he followed Kruse's example by shooting wide.
Gladbach took the lead with their next chance, again through Herrmann down the right, this time with Arango on hand to meet his cross and drill his shot in from the edge of the penalty area in the 28th minute.
Four minutes later, the hosts were celebrating a second goal when Arango's free-kick was headed into his own net by Ramos, under pressure from both Alvaro Dominguez and Kruse.
The game was effectively ended five minutes before half-time when Raffael made it three.
He exchanged passes twice with Kruse to be faced with only Thomas Kraft to beat, and he provided the perfect finish to a fine move with a lob over the Berlin goalkeeper.
Berlin lost belief and reverted to damage-limitation mode in the second half, succeeding at least in keeping the scoring down.
That was as much down to Gladbach's reluctance to attack them as their improved defence, although there were nevertheless a few chances for the Foals to net a fourth.
Arango was involved each time, first seeing Kraft make a last-minute dive to his right to push a 30-yard free-kick wide before he fell only inches short of reaching a lofted ball forward.
The damage had already been done in the first half, though, and there were no further scares for either goalkeeper as the clock was played down without the need for any stoppage time.