Tranquillo Barnetta scored the only goal of the game in Schalke's 1-0 triumph at home, which was also their first win over Gladbach in four matches.
The victory took Schalke to 34 points, one ahead of Gladbach and replacing Lucien Favre's men in third in the Bundesliga, while it continued the unbeaten resumption for Di Matteo's men, who have faced Hannover and leaders Bayern Munich in their previous two games since the winter break.
Di Matteo has been pleased with how his side has handled the absences of the likes of Klaas-Jan Huntelaar (suspension), Julian Draxler (hamstring) and Jefferson Farfan (thigh).
"We're missing a lot of players at the moment but we don't want to complain," the coach told Schalke's website after the win.
"Every single individual out there on the pitch tonight gave their all to get the three points. I'm proud of the boys.
"We can be very happy with our start to the second half of the season. We've picked up seven points against three strong opponents."
Di Matteo added: "We're delighted with the win. Monchengladbach are a very tricky side to play against and Schalke have struggled against them of late. Previous results against Borussia haven't exactly been positive.
"Fortunately, things were different this time. We were very well organised, hardly allowed anything through and scored the decisive goal. Our team showed a real desire to win."
While Schalke extended their unbeaten run to five games, Gladbach's perfect restart - they had defeated Stuttgart and Freiburg before travelling to Gelsenkirchen - ended thanks to Barnetta's 10th-minute strike.
The Swiss midfielder timed his run perfectly to get on the end of Kevin-Prince Boateng's cross from the right, volleying the ball home from inside the six-yard box.
"When you don't allow many chances, it becomes very difficult for the opposition," Barnetta said.
"I was glad to be able to show what I can do once again. The head coach gave me a chance and I have repaid his faith in me by scoring the winner."
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