Chris Zebroski gave County a first-half lead before Sam Clucas levelled things up in a second half which saw both sides reduced to 10 men.
A niggly encounter saw four more players booked with referee Dave Phillips forced to show his first yellow card after just seven minutes.
Mansfield created chances in the first half but both Clucas and Matt Rhead, who would later see red for the Stags, were denied from close-range by goalkeeper Lenny Pidgeley.
Zebroski made them pay for those missed chances after 30 minutes. The striker's glancing header from Adam Chapman's corner was his fourth goal of the season since joining the Welsh club in June.
Newport held on until half time but Mansfield equalised after 67 minutes when Clucas headed Ben Hutchinson's deflected corner inside Pidgeley's far post.
Tempers then spilled over as tensions rose. Lee Minshull was ordered off for striking Martin Riley in the face with his elbow.
But the Stags' numerical advantage lasted just four minutes before Rhead received a second yellow card.