Goals in either half from Jackson Irvine and Brian Graham earned them all three points.
Motherwell's late response began with Stephen Pearson's fierce strike.
But Scott Fox saved from James McFadden and brilliantly kept out a Keith Lasley drive to frustrate Motherwell.
It was a pulsating finish to a game that only sparked into life when Irvine fired in the opening goal.
The Australian was only drafted into the starting line-up minutes before the match because of an injury in the warm-up to Martin Woods.
And he made a great case for his inclusion when he deftly controlled a deep corner before lashing the ball past Connor Ripley, despite the best efforts of Kieran Kennedy on the line.
Fox saved well from a Louis Moult header and Chris Cadden as Motherwell tried to mount a swift response, but County regained the ascendancy at the start of the second half.
Playing principally on the counter-attack, they went close on a number of occasions, with Michael Gardyne having a header cleared off the line and passing up another great chance with a low drive that was blocked.
They got the second goal their play deserved when Graham slotted past Ripley as the Motherwell defence failed to deal with a Stewart Murdoch cross.
That looked like game over until Pearson's late strike - the midfielder blasting past Fox from 12 yards.
But the keeper was sharply off his line to prevent McFadden's lob beating him and he sprung to his right to deny Lasley a spectacular equaliser.
The result leaves Motherwell just a point above the relegation play-off spot and County in good spirits ahead of next weekend's League Cup semi-final against Celtic.
Ross County survived a late onslaught from Motherwell for their first league win of 2016, moving them up to fourth in the Premiership.