Sean O'Hanlon scored against his former club to keep play-off chasers MK Dons on track and leave struggling Swindon five points from safety.
The Dons took the lead when O'Hanlon headed home from Peter Leven's corner.
Calvin Andrew went desperately close to an equaliser when his powerful effort came back off the crossbar in first-half stoppage time.
O'Hanlon almost added a second before Andy Frampton was sent off for the Robins for a second bookable offence.
Swindon manager Paul Hart told BBC Wiltshire:
"We didn't start well. It's a poor goal to give away but he (the Swindon defender) was pushed.
"I thought we, overall, defended pretty well, we've hit the bar and had a penalty turned down.
"I can see we weren't at our best but we should have got something from the game."
MK Dons manager Karl Robinson told BBC Three Counties Radio:
"I don't think the headlines will say 'classic', but it's a win, it's a marvellous victory.
"What it's done is shown we can battle as well, yes we rode our luck at times but every good team has to do that.
"We didn't look as fluent as we have but when I get back in my car I'm sure I'll have a big smile on my face."