They bagged three sizzling tries in an 18-11 win to take revenge for last season's defeat in Dublin.
Boroughmuir winger Rory Couper was the hero with the touchdown that turned the contest.
The Irish had swept into the lead at Meggetland with two penalties from Dundee's Andy Thomson.
Glasgow Hawks' Murray Strang replied with a penalty before Richard McArthur grabbed a try for the visitors.
Then tries from Marc Teague, Couper and Steve Lawrie sealed it for the Scots.
Scotland's Under-20s lost 31-8 to their Irish counterparts at Falkirk Stadium.