Stevenage grabbed the points after a grandstand finish saw them snatch the win with three goals in the final eight minutes.
The smash and grab from the home side proved hard on Tamworth, who looked to have done enough to secure the win should have eased their fears of relegation.
There was no sign of the drama to come as both teams played out the first half which was devoid of chances.
Free-kicks proved to be the best opportunity for both sides to break the deadlock with Stevenage's Dean Brennan seeing an effort deflected wide on the half-hour, while Mark Cooper blasted just past the post with a 25-yard effort just five minutes before the interval.
The second half began with much more promising entertainment and Anthony Elding could have put Stevenage ahead within a minute of the restart after his close-range shot was blocked by Lambs keeper Wayne Henderson.
Stevenage also came close when Steve Watson was free in the area, but his effort from the six-yard box was blasted well over the bar.
It looked as if the home side would be punished for these failings when Tamworth took the lead on 69 minutes as Cooper chipped the ball neatly into the back of the net after a free-kick was awarded on the edge of the box following a foul on sub Brian Quailey.
Stevenage manager Graham Westley appeared to have made the unpopular decision to bring off midfielder Brennan for youngster George Boyd, but it proved to be a move which paid dividends as Boyd was in the thick of the home side's dramatic recovery.
Sub Boyd was provider on 82 minutes when his cross in from the left found Elding who headed home for the equaliser and less than two minutes later a Boyd free-kick in the area was powerfully headed home by Dino Maamria, who put Boro in the lead.
Further salt was rubbed into Tamworth's wounds when Lee Ayres committed an unnecessary push on Jon Brady as the Stevenage man made a hopeless chase for the ball in the Tamworth area.
Ayres was booked for his troubles and Maamria made the most of the resulting penalty to give Stevenage a victory which at one stage had been highly unlikely.