Matt Derbyshire showed his predatory instincts to sweep the home side ahead after just 90 seconds at the City Ground.
Derbyshire then curled an effort just wide of the far post from 20 yards in the 26th minute as Forest looked to extend their lead.
Birmingham introduced Jordan Ibe at the break to inject some pace into their attack, but it was Forest who should have gone 2-0 ahead early in the second period when Paterson raced through on goal, only to see his shot saved by Darren Randolph.
Ibe was involved on the hour mark, and the Liverpool loanee was unlucky to see his curling effort from just outside the box sail wide.
Birmingham began to turn the screw as the game approached full time as Chris Burke sent a good low ball across the face of goal, but it evaded all three attackers who slid in to try and convert it.
With 10 minutes left, Darlow flung himself across goal to save magnificently from Paul Robinson's point-blank header and Forest held on to win.