But a needless penalty before half time reduced the gap to 10-6 before a series of errors led to Andy Goode's try straight after the restart.
There was still a chance for Gloucester to reclaim the upper hand but they ran slap bang into one of the Aviva Premiership's most miserly defences before another basic error led to Marcel Garvey's killer score.
Credit to Worcester who pounced upon the errors and whose set piece was rock solid throughout. Their defence was also first class on the day. They did the basic things well.
It's not always appropriate to say that one man can change a game but the half time introduction of Andy Goode certainly looked to be the catalyst for the Warriors.
Within minutes of the second half restarting, Worcester had turned a 10-6 deficit into a 16-10 lead with Goode contributing all the points and never looked back.
Their renowned defence then kept Gloucester at bay, repelling several decent close range attacks before pouncing upon a turnover and scoring from range to really take the game away from the Cherry and Whites.
It was an incredible turnaround as Gloucester had looked so in control in the first half and a rare away win looked on the cards.
However, the nature of the Worcester comeback left Gloucester almost blinking in disbelief although Jonny May's late try at least earned a losing bonus point.
Defeat will come as a bitter blow though especially given the platform laid in the first half and a tough week lies ahead with a trip to next up.
Conditions were set fair at Sixways. There was no hint of rain although there was a stiff breeze blowing. Both sides came out as announced meaning Alex Brown made his first start since September 17th at Harlequins.
It was a bright opening from Gloucester who were quickly looking to put some width on the ball but got little change out of a rugged Worcester defence.
The home side's first attack was a promising one as they pushed Gloucester back well into their own 22 until great work from Mike Tindall stripped the ball in the tackle to ease the pressure.
Gloucester dominated the next few minutes without really threatening to break through and settled for a penalty from Freddie Burns on 11 minutes to open the scoring.
Not rolling away from the tackle area though promptly gave Joe Carlisle a chance to respond and the left footed fly half made no mistake to level the scores after 14 minutes.
Sleight of hand from Carlisle then almost opened up the Cherry and Whites as Mile Benjamin powered through the middle but the defence held - just. The first quarter ended with little to choose between the two sides.
However, the fly half's handling error almost cost the Warriors as Gloucester hacked downfield and followed up well but the home defence regrouped just in time to end the danger.
The Gloucester eight then sapped the energy out of the Worcester pack with a fine drive before the ball was released wide and Charlie Sharples seemed to make the corner after breaking a tackle and the TMO awarded the score. Burns added a superb touchline conversion.
If anyone deserved a positive TMO call it was Sharples who had been denied three times in recent weeks by the replay and Gloucester had a spring in their step.
Burns was starting to take the game by the scruff of the neck and rolled a couple of lovely touchfinders into Worcester territory to keep his side moving forward and in the right areas of the pitch.
Both teams tried to force the pace as half time approached and both sides looked to be building momentum in attack until poor handling killed promising moves but the Warriors finished the better as they scored a penalty with the last kick of the half to send the teams in at 10-6.
Gloucester had enjoyed the better of the first half but had perhaps been guilty of trying to move the ball wide too quickly.
A 10-6 lead at the break was a half decent return but the home side had shown enough to keep Gloucester well and truly on their toes in the second half.
In fact, Gloucester didn't help themselves as the second half began as Marcel Garvey gathered the restart and evaded tacklers to get his side on the front foot and launch incessant pressure in the Gloucester 22.
Andy Goode had replaced Joe Carlisle at half time and badly scuffed an attempted drop goal only to be called back for a penalty which struck the right hand upright and stayed out. Worcester gathered the rebound and the pressure continued.
And the try followed as Goode stepped inside his man from quick scrum ball and his stretch just made the line. He converted himself as Sixways erupted as Worcester took the lead for the first time.
Gloucester looked for an immediate response and good work from the backs set up a possible catch and drive opportunity but a knock from Scott Lawson when well placed ended the threat.
The momentum had certainly changed and things continued to go Worcester's way as Morgan lost the ball in contact as he tried to burst into the home 22. Goode hacked downfield and Morgan had to leave the field on a stretcher injured.
When Gloucester were then penalised for a high tackle on the diminutive Jonny Arr, Goode extended the lead to 16-10.
Bryan Redpath's team just hadn't got going in the second half and another botched catch and drive attempt only heightened the frustration.
A missed kick to touch from Goode though gave Gloucester a glimmer of hope as Simpson-Daniel countered and May took it on at pace but still the breakthrough remained elusive.
And as Gloucester pushed, a fatal error came. Henry Trinder misplaced a grubber in the Worcester 22 with the ball hitting Marcel Garvey and bouncing up kindly for him to run it back all the way for a 21-10 lead as Sixways went into raptures.
Goode missed the conversion and a 71st penalty to at least put a dent in his impeccable afternoon's work but Gloucester still had a mountain to climb.
Gloucester didn't throw in the towel and Jonny May's 78th minute try offered a glimmer of hope but there was no fairytale comeback on the cards and Gloucester were left to reflect on one that slipped away.
|Worcester Warriors Score Card|
|Gloucester Rugby Score Card|