Carlo Nash made his debut in goal for Boro, while the only players with real first team experience were Andrew Davies, Mark Wilson, Allan Johnston and Stewart Downing.
Boro dominated the first half but could only manage a 2-1 lead at the break.
Mark Wilson converted a penalty after 20 minutes and Jamie Cade extended the lead shortly before the break, although Birmingham did have time to reply through Bryan Hughes on the stroke of half-time.
Birmingham faired better in the second half but couldn't break down a stubborn Boro defence.
It was no surprise when Boro wrapped up the game with a third, Downing striking a superb free-kick past the Blues keeper, Ian Bennett.
That's two wins from two for the Reserves, I know it's early days but can they go one better than last season and lift the Premiership Reserve League (North) trophy.
Boro squad:
Nash
Close
Taylor (Masters)
Gulliver
Davies
Smith
Wilson
Johnston
Downing
Cade (Graham)
Doven (Nordgren)