County undone by a late penalty in South London.
Goalkeeper Rhys Taylor, who returned to the Club from his loan spell at Wrexham, was included in the starting XI, making his Football League debut for Exiles in the final game of the season.
Dangerman Akinfenwa was involved in the opening minutes of the game, touching down a long-ball forward and advancing into the County area before firing his volley over the crossbar.
Both sides looked to play attacking football and Scott Barrow was set free down the left-wing by a flicked header by Lenell John-lewis and his cross was met by Scott Boden, who glanced his header just the wrong side of the post.
The home side looked a threat in the area and just after the twenty-minute mark Rhys Murphy received the ball from a knock-down and fired a powerful volley towards goal that was charged down by Andrew Hughes.
Just before the half-hour mark there was a lengthy stoppage to play as Connor Smith clashed heads with Lenell John-Lewis and required treatment on the pitch before leaving the field on a stretcher.
Inside first-half stoppage time, Scott Boden found room in behind to Wimbledon defence to chip a dangerous ball into the area that found Lenell john-Lewis, but the striker couldn't connect cleanly with his volley and the home side were able to clear.
After the break, County were able to start the final forty-five minutes of the season brightly. A measured ball forward by Danny Holmes was met by Lenell John-Lewis, who was able to hit a driven effort that Shea was forced into pushing away from danger.
Just after the hour mark Rhys Murphy was allowed the space to generate a forceful volley from just inside the area that required Rhys Taylor to be alert to tip his Murphy's effort over the crossbar.
As the game neared eighty minutes County were able to capitalise on a scramble inside the area, which resulted in the ball dropping kindly for Alex Rodman, who had his close-range effort stopped by a good reaction save by Shea.
With little over ten minutes to go, substitute Olusanya was allowed room to advance into the area and went down under the challenge of Ben Davies. The winger dusted himself off to calmly slot the spot-kick past Rhys Taylor to give the 'Dons the lead.
Into stoppage time and County introduced Tom Meechan to add more firepower up front, but were unable to carve out an opportunity to snatch a late equaliser.
FiNAL SCORE: AFC WIMBLEDON 1 - 0 NEWPORT COUNTY
Away attendance: 402