Roman Golobart and Gregory Tade struck early in the second half for the hosts but they had to cling on at the end after Aberdeen substitute Rory Fallon’s 76th-minute goal.
Butcher, whose side are now four points clear of the division’s bottom two sides Hibs – who Inverness face on Wednesday – and Dunfermline.
Butcher said: “Twenty-one games and no clean sheets speaks for itself, but against Aberdeen that was our 13th different back four that we’ve used this season.
“Getting the second goal was important, but I think everyone, from the supporters to the players and even the management, started thinking about that Dundee United game [when they lost after being 2-0 up] when Aberdeen pulled a goal back. You get worried that it could happen again, but the boys were really resolute in the way they defended late on.”
Aberdeen boss Craig Brown said: “We feel St Mirren are catchable, but they got a result against Rangers, so we’ve missed an opportunity.”