The hosts capitalised on their numerical disadvantage in the closing stages of the first half - albeit under controversial circumstances.
Nevertheless, Aitor Karanka's men remained within one goal for much of the second half despite their disadvantage, and Boro were duly rewarded for their resilience.
Dean Whitehead, starting his first league clash since October, smashed home from close range to restore parity on 74 minutes following a swift counter-attack by the visitors.
Steve McClaren's charges forced the issue and were ultimately rewarded, as Sammon pounced in the dying embers to steal all three points.
Consequently, Derby move fourth in England's second tier and strengthen their grip on a playoff place.