Weymouth, who were down to 10 men at 67 minutes - following Nathan Carlyle’s second yellow offence - found victory in the 88th minute.
Substitute Cam Murray’s strike sailed past the Rebels’ defence and found the bottom corner of the goal.
A slow start to the game meant there were no real chances until the tenth minute. Matty Lench’s corner which fell to the feet of Joe Dandy, resulted in a goalmouth scramble from Weymouth, who eventually cleared their lines.
On 35 minutes, Rhys Forster made an emphatic save to deny Mitch Parker from giving Weymouth the lead.
However, three minutes later, an apparent handball by Joe Dandy meant the Terras were awarded a penalty, ultimately converted on the spot by Bradley Ash.
On 57 minutes, Teddy Howe doubled Weymouth’s lead. Less than two minutes later, Slough super-sub Arnold Matshazi curled one past Zaki Oualah, shifting the momentum of the game.
Dan Roberts had two chances to equalise for the Rebels, with one shot just wide of the post and another floating onto the roof of the net.
But it wasn’t long until the breakthrough happened. Following Carlyle’s red card, Scott Davies made things level with a beautiful free kick that glided over the wall.
With everything level at 70 minutes, a fruitful twenty minutes ensued with an array of chances from both sides.
Weymouth came close to retaking the lead after Tom Bearwish’s close-range effort hit the post.
With 10 minutes left on the clock, Lench’s attempt to propel Slough into the lead was blocked in the penalty area.
Spurred on by the change in tempo, the Rebels had another close chance in the 83rd minute, after Aaron Kuhl hit a powerful shot from the edge of the box that narrowly went wide.
In the 88th minute, Murray’s goal settled the final score to the delight of the travelling away fans.
Despite four minutes of additional time, Slough failed to find a breakthrough to equalise and the game finished 2-3.
Slough will face Dartford at home on Tuesday night and will be aiming to get back on track after three consecutive defeats.
Weymouth Line up
Zaki Oualah, Teddy Howe, Harry Kyprianou, Alexander McBurnie, Dan Matzuaka, Nathan Carlyle, Bradley Ash (Ben Gerring 68), Ahkeem Rose (Keelan O’Connell 68), Tom Bearish, Mitch Parker (Cam Murray 68), Tom Blair. Unused substitutes: Josh Oyisan, Tyler Forbes.