Schalke failed to replicate their Champions League form from midweek, when they beat Hapoel Tel Aviv 3-1, and despite some good opportunities for Raul and Klaas-Jan Huntelaar were lucky to take a point after Halil Altintop missed a late chance for Frankfurt.
Schalke, last season's runners-up who spent millions of euros in the close season, are 15th in the league on six points after drawing three of their past four matches and losing the other.
"I can only smile because we are lucky to get away with a point," Schalke coach Felix Magath said. "We trembled for a long time. I cannot be satisfied with our game."
Werder Bremen took a fifth-minute lead through former Gladbach player Marko Marin. The Brazilian Wesley added another seven minutes later, when he ran almost the length of the pitch without being challenged to fire home.
The hosts were taken by surprise early in the second half, with Germany international Aaron Hunt's deflected shot beating keeper Logan Bailly. Moenchengladbach cut the deficit via a Per Mertesacker own goal.
Peruvian Claudio Pizarro sealed Bremen's win in the 75th minute with his 134th Bundesliga goal, a record for a foreign player.
Cologne suffered a further setback in their bid to stay up, losing 2-1 at Hanover 96. Ivorian striker Didier Ya Konan scored twice to take his season's tally to five goals.
VfL Wolfsburg's lacklustre start under former England coach Steve McClaren continued when the 2009 champions slumped to 2-1 defeat to Nuremberg. Wolfsburg are 13th with 10 points.
FRANKFURT CONTROL
Schalke started well and threatened with Raul, who launched a quick counter-attack but saw his close-range effort saved by Frankfurt keeper Oka Nikolov.
The Bulgarian came to the rescue again just before the break when he denied Huntelaar.
Frankfurt took control in the second half and should have punished the visitors in the 69th minute as they pounced on a defensive error, but Halil Altintop managed to fire over the bar from two metres despite an empty goal.
"From the 46th minute onwards the game was under our control," Frankfurt coach Michael Skibbe said. "It is that domination that did not allow Schalke to develop their game. We were outstanding today."
Champions Bayern Munich escaped on Friday with a 0-0 draw at Hamburg SV, who moved up to fifth spot on 15 points.
