Forest Green's recent form had been a strong indication that they can avoid relegation this season, but they slipped to a dismal defeat against the Lambs.
Having gone behind to a Peter Folkes strike in the 33rd minute, the home side fought back bravely.
Paul Wanless levelled for Rovers with a precision strike, but Tamworth have their own relegation worries and were desperate to snatch three points.
So much so that they dug in to grab their first victory in eight games, easing their relegation fears in the process.
The Lambs went ahead after 33 minutes when an inswinging corner was flicked on by Nathan Jackson and Folkes managed to force the ball home inside the six-yard box.
Ryan Clarke soon denied Carl Heggs, but in the 74th minute Wanless equalised from close range and Rovers sensed their second victory in four days.
But Danny Davidson drilled home with 13 minutes left before Matthew Williams added a third late on.
Defeat was hard to swallow for Rovers, for a point would have been a much fairer reflection on proceedings.
However, victory for Tamworth after their memorable FA Cup run was just reward for their desire and commitment to remain in the division.
Both clubs still have plenty of hard work left to do if they are going to get themselves out of trouble, but Tamworth have definitely given themselves a welcome head start.