The 67-year-old delivered an unlikely 10 points from 12 as the Millers launched a survival bid and he becomes the first ever Millers winner of the award at this level and the first at any level since Andy Scott in August 2011.
They started off with a 1-0 win at Sheffield Wednesday, becoming just the second side to triumph at Hillsborough this season, while following it up with another superb 1-0 victory over Middlesbrough three days later.
Things looked like coming to a halt as Derby surged into a 3-0 lead in their next match, but a heroic rescue act saw them score three goals in the final eight minutes to draw 3-3.
They rounded the month off in fine style with a third 1-0 success over a promotion-chasing side, this time against Ipswich at Portman Road.
Warnock beat former Millers boss Steve Evans, Sean Dyche of Burnley and Cardiff's Russell Slade to the award - his ninth since 2000.
