Marcus Allback, who has struggled to make an impact at Aston Villa this season, produced his best performance since his arrival last summer with two opportunist goals.
It ended Villa's worst run of the season and earned the Midlands club their first win eight matches – much to the relief of manager Graham Taylor.
The defeat was a setback to Chelsea's European aspirations but they were outgunned on this occasion as Villa finally cashed in with one of their best performances of the season.
Chelsea's pre-match fears about the danger of Darius Vassell were fully justified as the England striker did much to break down the Londoners' resistance.
Allback cashed in with a match-winning display which should guarantee him remaining at Villa Park next season.
Fourth in the table Chelsea paid dearly for some indifferent tactics.
They put Jimmy Hasselbaink on the substitute's bench and their attacking options appeared limited in the early stages when Villa were often the more dangerous.
Vassell was always prominent and the pre-match fears of Chelsea manager, Claudio Ranieri, came home to haunt him as the England striker made several good moves as the Londoners defence struggled to contain him in the difficult windy conditions.
Gareth Barry was also in the thick of the action in this crucial spell and it was fitting he began the move which led to Villa storming ahead in the 11th minute.
A cross-field pass from Barry was fed to Oyvind Leonhardsen and his centre was breasted down by Barry into the path of Allback to smash home only his second Premiership goal of the season.
Chelsea responded with some good attacks but their best chance of a first-half equaliser was a free-kick which was confidently handled by Peter Enckelman.
Villa should have increased their lead in the 27th minute when substitute Steve Staunton put J Lloyd Samuel clear down the left but Vassell attempted to side-flick the ball past Carlo Cudicini and wasted a fine opportunity.
Chelsea moved back into the game in the closing stages of the second half but they were extremely fortunate in the 49th minute when John Terry slipped as he challenged Vassell.
The Villa striker flicked the ball onto Rob Edwards and the young Welsh international saw his clever chip clip the crossbar.
Villa delighted their fans with the quality of football and a one-two between Allback and Staunton ended with the veteran Irishman shooting just wide.
Enrique De Lucas was no better when an equally good goalscoring opportunity presented itself but he too blasted his shot wide of the target.
As a result Chelsea struggled to come to terms with Villa who put the issue conclusively beyond doubt in the 79th minute when the revitalised Allback turned and hooked the ball into the net following a headed pass from Vassell.
But two minutes from time Terry moved up to head home a Hasselbaink corner to produce a tense finish for the anxious Villa fans.