With six minutes remaining on Saturday, the defender got on the end of Kallum Higginbotham's cross to head home from close range and end a run of eight straight defeats at Rugby Park.
Vitalijs Maksimenko had given the hosts a 55th-minute lead, which was cancelled out shortly afterwards by Higginbotham.
During a goalless first 45 minutes, both sides had chances to open the scoring.
First, Thistle's James Craigen struck the bar from inside the box, while Manuel Pascali headed narrowly wide for the hosts on 15.
The second half was a much more entertaining contest, with both sides coming close inside the opening seven minutes.
Partick's Prince Buaben went close from outside the box while, at the other end, Paul Gallacher saved well from Jackson Irvine.
And it was Maksimenko who broke the deadlock 10 minutes after the break when he lashed home a low shot from six yards following Alexei Eremenko's corner.
But within three minutes, Partick were level through Higginbotham who located the bottom right-hand corner of the net with a curling 22-yard free-kick.
Kilmarnock came mighty close to going back in front shortly afterwards with Michael Gardyne striking the bar from all of 30 yards.
And the hosts continued to create chances with Gardyne narrowly heading wide on 66, while Ross Barbour had an effort cleared off the line by Conrad Balatoni.
But with 84 minutes on the clock, Taylor-Sinclair sealed the win to move Partick out of the relegation play-off spot.
However, Killie came close to snatching a late equaliser with visiting keeper Paul Gallacher pushing away a dipping volley from Barbour.