Sydney - Scott Staniforth and Cameron Shepherd scored second-half tries against their former team to lead the Force to a 15-14 win over the Waratahs in Super 14 rugby on Saturday.
Staniforth's 37th career try gave the Force a one-point lead which they held through the final 14 minutes.
Shepherd, also a former winger with the Waratahs, gathered in a chip kick in the 50th minute for his fourth try of the season and Wallaby flyhalf Matt Giteau converted which put the Force up 10-9.
That lead lasted only two minutes after Will Caldwell, who became the Waratahs' most-capped lock with 64 matches, scored an unconverted try just minutes after coming out of the sin-bin.
The win completed an all-Australian sweep for the Force after earlier victories over the Brumbies and the Reds.
Wide of left post
It was also the Force's first win over the Waratahs since joining Super rugby in 2006.
"It's a great milestone for the club," Force coach John Mitchell said.
The Waratahs led 9-3 at half-time on three penalties by Daniel Halangahu in the 16th, 20th and 28th minutes, while Giteau replied with a penalty for the Force with six minutes left in the half.
Shepherd's 49m penalty attempt for the Force in the final minute of the opening half was just wide of the left post. It came after Caldwell was given a yellow card for a high forearm tackle on scrumhalf Josh Valentine.
The Force had the best of the early scoring opportunities and had two tries called back.
Staniforth grabbed a Giteau cross-field kick, then booted downfield for Drew Mitchell to regather and cross the tryline. But Staniforth was ruled to have put a foot into touch, although replays suggested he stayed in the field of play.
Earlier, the Force's James O'Connor made a 60m midfield burst but was correctly ruled by the television match official to have been tackled into touch before getting the ball down.
The Force was coming off a one-point loss last week at home to the Hurricanes, who rallied from a 14-point deficit to defeat the Force 28-27 on fullback Cory Jane's try in stoppage time.
Force captain Nathan Sharpe said his team did a good job of putting the disappointment of the close loss behind them.
"We'll take that one," said Sharpe. "We knew what we were going to expect - a slugfest - and we got one."
The Waratahs, within sight of a semi-final spot, have a bye next weekend before three matches in South Africa to close the season.
Waratahs captain Phil Waugh said his side made far too many mistakes.
"You're not going to win games if you leave that many points on the field," Waugh said. "We have to regroup and freshen up before we go to South Africa. We need to win them all."
Force: 15 (Scott Staniforth, Cameron Shepherd tries; Matt Giteau penalty, conversion).
Waratahs: 14 (Will Caldwell try, Daniel Halangahu 3 penalties). HT: 3-9.