The Force held out last year's Super Rugby Champions the Bulls for a 26-21 victory in Perth for their second victory in a row.
The loss was the Bulls third in a row after losing to the Crusaders, Reds and now the Force and all but rules out the Bulls chances of retaining their title this year.
The Bulls have played nine and lost five matches in total and trail the Sharks by 7 points but that could be extended if the Sharks win later in this round.
Wallaby winger James O'Connor was again the star of the show and kicked five penalties to Morne Steyn's four. Willie Ripia added a penalty while O'Connor was in the sin bin for a lifting tackle on Bulls fullback Zane Kirchner.
The Bulls outscored the Force by two tries to one but their discipline cost them dearly as South African referee Mark Lawrence penalised their indiscretions.
Tries by South Africa internationals Chiliboy Ralepelle and Bjorn Basson helped put the Bulls 15-12 up at halftime at nib Stadium.
But Force center James O'Connor, who kicked three penalties in the first half, added three more after the break while fullback Cameron Shepherd scored a decisive try in the 67th minute, giving the Force a 26-18 lead and sealing the side's first home victory this season.
Morne Steyn booted his third penalty of the match late on to complete an 11-point haul and earn the Bulls a bonus point, but the South African team's hopes of reaching the playoffs took another hit.
The visitors came into the match having suffered back-to-back defeats but looked on course to end a miserable run on their three-game road trip by going 12-6 up by the 20th minute.
Springboks hooker Ralepelle canceled out a fourth-minute penalty by O'Connor by picking the ball up after an initial forward thrust by Francois Hougaard and falling over the line by two meters.
O'Connor then kicked another penalty in the 17th, before being sin-binned for an illegal dump tackle on Zane Kirchner.
In the Australia winger's absence, the Bulls scored 10 points, with Basson breezing through a gap in the defense to cruise under the posts after scrumhalf Fourie du Preez had darted off the back of a rolling maul.
Steyn converted and, after Willie Ripia landed a penalty for the Force, kicked one of his own for 15-9 in the 28th minute.
O'Connor returned from his 10-minute sanction to put the Force just three points in arrears at the break but the Bulls started the second half well and almost grabbed a third try when Stephan Dippenaar put his foot in touch just as he was diving over the line to ground in the right corner.
Steyn's penalty in the 55th was the Bulls' only reward for their dominance before the Force fought back.
O'Connor kicked two more penalties in the space of four minutes to remain perfect with the boot and level the scores.
Shepherd finished off a series of phases by going over in the corner before O'Connor's 76th-minute penalty ended the hopes of the Bulls, who at least went home with a bonus point thanks to Steyn's late kick.
The Pretoria-based side is seven points outside the top six after nine games.
Final Score Force†26 Bulls†21
Tries - C Shepherd
Pen - J O'Connor 5, W Ripia
Cards - J O'Connor (18th min) yellow
Tries - C.Ralepelle, B. Basson
Con - M Steyn 4
Referee: Mark Lawrence (South Africa)
Assistant referees: Andrew Lees (Australia), Julian Pritchard (Australia)
Television match official: Matt Goddard (Australia)
Force : 1. Pek Cowan,2. Ben Whittaker,3. Matt Dunning ,4. Sam Wykes,5. Nathan Sharpe (Captain),6. Richard Brown,7. Jono Jenkins,8. Ben McCalman ,9. Brett Sheehan,10. Willie Ripia,11. Rory Sidey,12. James O'Connor,13. Patrick Dellit14. Nick Cummins ,15. Cameron Shepherd
Reserves:16. Nathan Charles ,17. Kieran Longbottom ,18. Tom Hockings,19. Tevita Metuisela,20. Mark Swanepoel,21. Mark Bartholomeusz,22. Alfie Mafi.
Bulls :Zane Kirchner, Bjorn Basson , Stephan Dippenaar , Wynand Olivier, Francois Hougaard, Morne Steyn , Fourie du Preez, Pierre Spies, Dewald Potgieter, Deon Stegmann , Victor Matfield (c), Bakkies Botha , Werner Kruger , Chiliboy Ralepelle , Dean Greyling .
Replacements: Gary Botha , Rossouw de Klerk, Flip van der Merwe, Danie Rossouw , Derick KuŁn ,Jaco van der Westhuyzen, Francois Brummer .