Late goals from Graham Zusi and Dominic Dwyer helped Sporting KC to victory against second-bottom Chicago in front of 18,938 fans at Sporting Park.
Zusi broke the deadlock 10 minutes from the end before Dwyer made sure of the points in the second minute of injury time as Sporting KC, who moved second in the Eastern Conference momentarily, snapped their three-game losing streak at home.
The result was enough for Sporting KC to book their spot in the play-offs for a fourth consecutive campaign, having collected 49 points with two regular-season matches remaining in the East.
Sporting KC had a golden opportunity to open the scoring in the 13th minute after Benny Feilhaber was fouled inside the penalty area, but Dwyer fired his effort over the crossbar.
At the other end, Sporting KC goalkeeper Andy Gruenebaum got down low to deny Fire forward Quincy Amarikwa and push the ball away for a corner.
Feilhaber came close to putting Sporting KC ahead, but his shot cannoned off the post and into the arms of Chicago keeper Sean Johnson.
After a scoreless opening half, the home side eventually made the breakthrough courtesy of Zusi with 10 minutes remaining.
Zusi charged towards the box before curling the ball into the top corner from the edge of the area.
And Dwyer made amends for his earlier penalty attempt, nodding home his 21st goal of the season in the closing minutes and extending the Fire's winless streak to seven matches.
Meanwhile, Seattle Sounders missed the chance to move clear of Los Angeles Galaxy in the Western Conference as Vancouver Whitecaps kept their play-off hopes alive.
Level on points with the Galaxy, Seattle were beaten 1-0 at home to the Whitecaps.
Kekuta Manneh's goal on the stroke of half-time was all that separated the two teams at CenturyLink Field.
The Sounders remain level on 60 points, though the Galaxy have a game in hand and are due to play Dallas on Sunday.
Vancouver reclaimed the fifth and final play-off spot in the West, moving one point ahead of Portland Timbers.
