After impressive draws away at Exeter and Bournemouth in the past week, this was a game that the Argyle youngsters were expected to win, but their visitors defended in depth, making it hard for their hosts.
The first-half was played almost exclusively in the visitors’ half, with Oscar Massey twice going close before Oscar Rutherford's driven cross was deflected on to the post.
Newport continued to throw bodies in front of Argyle efforts with Jeremiah Medine, Massey and Scott Crocker denied before the half-time whistle came to their rescue.
Argyle continued to surge forward after the break and Rutherford had the ball in the net only for his effort to be ruled out for offside.
The breakthrough had to come, and it did when great play by Crocker found the onrushing Will Jenkins-Davies firing across the goalkeeper and inside the far post on 65 minutes.
Chances came and went until Newport shook Argyle with an 80th minute equaliser from Lewys Twamley, the Exiles stand-out player, who had also featured in their senior side’s 3-1 defeat to Argyle in the Papa John’s Trophy just weeks earlier.
The Greens were not to be denied on this occasion, though, and the winner arrived four minutes from time, Jamal Salawu crossed from the left for Crocker to help the ball on to Rhys Shirley who showed good control before slipping his shot past the visiting keeper.
Darren Way said: "The majority of the first half saw us having the majority of the possession and chances as we controlled the game. If we could have scored we would have gone in at the interval leading by four or five goals.
"It was a case of regrouping and getting that first goal as we knew they (Newport) would tire.
"They equalised with their first effort on target but the lads responded we to get the second goal.”
Argyle: Lewis Moyle, Oscar Rutherford, Finley Craske, Charlie Miller (Jeffrey Forkuo), Ethan Mitchell, Angel Waruih, Jeremiah Medine (Jamal Salawu 55), Scott Crocker, Brandon Pursall, Oscar Massey (Rhys Shirley 55), Will Jenkins-Davies. Substitutes not used: Tyler Coombes, Ali Mansaray.