Villa, brilliantly served by Wilfred Bouma, are now unbeaten in their last eight games against Chelsea and were involved in their second draw of the season with the London side.
They produced an outstanding second-half performance and in the process collected their first point in five games to halt their dramatic decline.
But they were in no small way assisted by an off-key Chelsea, who are obviously struggling to recapture their match-winning form because of some indifferent finishing.
Didier Drogba was sadly out of touch and disappeared completely in the second half when Villa turned up the heat.
Frank Lampard too could not escape criticism. Like Drogba he missed a match-winning opportunity in the final five minutes which would have been an injustice to Villa's courageous display.
Chelsea's blend of talent badly needs refining and Mourinho is now desperate to find the right blend.
Chelsea's star-studded outfit were impressive but often gave the impression that they could win when they liked. But such self-confidence has a nasty habit of rebounding and the high-priced Stamford Bridge stars struggled to find their noted finishing power.
The story could have been different if Drogba had converted a reasonably easy opportunity in only the seventh minute. The Ivory Coast striker aimlessly lofted his shot over the bar from a cross by Michael Essien.
Essien was the player who forged forward to pose a lot of problems for Villa's defence, but the Londoners were far too casual to completely dominate the Midlands club.
Villa were rarely a real danger in the first half. Their one moment of possible glory occurred when young Craig Gardner, who had to limp off shortly afterwards, produced an excellent shot on the turn and Henrique Hilario was forced to make his one real save of the match.
On the other hand, Ashley Cole had a wonderful chance to put Chelsea ahead when Drogba cleverly picked him out at the far post but the England defender's header went straight to the waiting Gabor Kiraly.
Lampard was always on the lookout for a goalscoring opportunity, but he too was thwarted by teenager Isaiah Osbourne which generally summed up Chelsea's latest performance.
Even the introduction of record signing Andriy Shevchenko failed to produce the desired results in the second half when Villa gained in confidence to take the game to the opposition.
Chelsea became increasingly frustrated as Villa piled on the pressure in their spirited bid to snatch a win.
Gavin McCann was a major inspiration. Often he upset Chelsea's stars with his sometimes ruthless tackling but it did keep Villa in the game.
It was only when they realised that Chelsea were vulnerable that Villa came out of their shell in the second half.
They pounded Chelsea but the skill and ability of Ricardo Carvalho and Paulo Ferreira ensured that the Londoners at least shared the points.