Sam Foley's first-half winner helped Newport County climb one place to 16th in the Blue Square Bet Premier as they continued to battle the threat of relegation.
Victory could have been more comfortable for the hosts as they dented Mansfield's play-off hopes.
Foley was among those to waste chances for the hosts.
But he gave County their fifth win in six games as he converted Nat Jarvis' cross in the 33rd minute.
VIEWS FROM THE DRESSING ROOM
Mansfield Town manager Paul Cox told BBC Radio Nottingham:
"After that performance a few harsh words were needed to be said and I needed to question desire levels today.
"I just think we looked sluggish, I think we looked a yard off the pace all over the park, I don't think that work ethic was there today.
"We dust ourselves down, pick ourselves up and there's 15 games to go. Hopefully we'll try and rectify what went wrong today.
"When in possession we didn't look sharp and more than anything mentally we were a mile off the pace"
Sorry, we were unable to load match stats, please try again.