Tamworth eased past 10-man Lincoln for their first win in five games.
Kieron St Aimie, on loan from Kettering, found the top corner from 12 yards to open the scoring.
Imps defender Tony Sinclair was dismissed for his second caution after bringing down St Aimie in the area and Iyseden Christie scored from the spot.
Francino Francis headed in a Liam McDonald corner before St Aimie scored his second with a shot from just inside the box.
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Lincoln City manager Steve Tilson told BBC Lincolnshire:
"For 15 minutes we were on top but then we conceded a poor goal and all the momentum went out of the window.
"Their four goals were all down to poor defending. In the first half they were so direct and after the first 15 minutes we couldn't cope, it was like men against boys.
"Until today we'd only had one defeat in four and we were going the right way but a performance like that sets us back again. We haven't got the strength in depth and you can only do your best but we've let ourselves down today."