Dublin notched his 44th minute winner after being drafted into the side as a central defender in place of Ronny Johnsen.
The former England player took the match honours with his crucial goal scored with an over-head kick following a bad mistake by James Beattie.
It also silenced the critics of a small group of fans who demonstrated before the game against Villa's veteran chairman, Doug Ellis.
Southampton, the Premiership away draw specialists, battled in vain for a point but Villa were very determined to make amends for their recent results and deservedly emerged with a vital win.
Dublin was the matchwinner and also Villa's star man as he demonstrated his value with an outstanding performance despite a somewhat shaky start.
He had experienced several anxious moments against Kevin Phillips and James Beattie but neither Southampton striker could capitalise upon the early mistakes of the makeshift Villa defender.
Only a brave save by Antti Niemi kept out Darius Vassell, while Southampton's first threat was a cross shot from Anders Svensson which went just wide.
Juan Pablo Angel had a goal disallowed for offside and seconds later lashed a long-range shot onto back netting of Southampton's goal.
Villa pressurised Southampton at every opportunity but could not find a way through until Dublin's vital strike when he capitalised upon a massive mistake by Beattie.
The England striker mistakenly headed Gavin McCann's corner back towards his own goal and Dublin accepted the gift to break the stalemate to score with an over-head kick for only his second goal of the season.
Villa counted themselves extremely fortunate 13 minutes into the second period when Phillips produced a cross which beat everyone including Neil McCann at the post.
David O'Leary, Aston Villa's manager, said: "Our main objective was to get a win and this was achieved with Dublin's goal. We must score more often if we are to climb the table."
Gordon Strachan, the Southampton boss, said: "We could have had Thierry Henry and Ronaldo up front and they would not have had a chnace. Our first 45 minutes' performance was the worst I have seen from my side this season."