Kongsvinger – Sosha Makani and Mjøndalen were looking to clinch a play-off spot but fell short due to costly mistakes on the road against Kongsvinger.
Magnus Sylling Olsen had an excellent opportunity to put Mjøndalen in the lead in the 16th minute but his left footed shot was parried nicely by keeper Otto Fredrikson.
In the 33rd minute, the home side should have taken the lead when a header from point blank range by Fredrik Mani Paalerud went over the bar.
Seven minutes later it was the normally reliable keeper Sosha Makani’s mistake that led to a goal for Adam Gueven.
Kongsvinger were applying pressure when right back Erik Midtgarden sent a pass to Makani. The Iranian keeper had a bad first touch on the ball and Gueven dispossessed the ball from Makani and easily slotted the ball into the net to give Kongsvinger a 1-0 lead with five minutes remaining in the first half.
Christian Gauseth had a chance to equalize for Mjøndalen early in the second half but his shot inside the penalty area went high over the bar.
Twenty minutes remained on the clock when Paalerud took advantage of a mistake by left back Joachim Solberg Olsen and sent a cross near the goal that was finished off nicely by Gueven for his second goal of the match as Kongsvinger increased their lead to 2-0.
Joachim Solberg Olsen made amends for his mistake when his long cross from the left was headed off the post and into the net by Jonathan Lindseth to cut the lead to 2-1 in the 86th minute.
Three minutes later Makani made a great save to deny a free kick but Spanish forward Maikel tapped in the rebound to give Kongsvinger a 3-1 victory.
Two matches remain on the season and Mjøndalen will be looking to bounce back with a win when they host KFUM Oslo on 23 October.
A win for Mjøndalen will be enough to clinch a play-off spot as they continue their quest to return to the top flight of Norwegian football.