Padraig Amond bagged his third goal in two games to help fire Accrington to their first away win of the season.
The 23-year-old, on loan from Portuguese side FC Pacos de Ferreira, tapped in Bryan Hughes' low cross after just three minutes.
The Dons conceded a carbon copy when the unmarked Craig Lindfield tucked in Dean Winnard's centre from close range.
Ian Dunbavin saved substitute Brendan Kiernan's late curling effort to leave the Dons winless in eight.
VIEWS FROM THE DRESSING ROOM
AFC Wimbledon manager Terry Brown told BBC London 94.9:
"A real soul destroying defeat, credit to Accrington who did a real job on us.
"We conceded our customary two early goals and never really looked like breaking down the opposition.
"I thought the first half it was men against boys. Second half we had a bit more fire in our belly but we lacked a cutting edge and a drive. It is my job to lift this group."