Darko's move to Kingsmeadow sees him link up with former City academy boss Neal Ardley, who became manager of the npower League Two club earlier this season.
The 19-year-old striker will remain with the Dons until March 23.
He told their official website: "All season I have been trying to get out on loan and get first-team games under my belt.
"I am looking to do what I can for the team and help Wimbledon stay up.
"I worked with Neal Ardley for three years and he knows what I am like as a player. He knows that I will work hard for the team and do my best to help the club in this situation."