Chris Templeman scored Forfar's winner as they recorded their first away win of the season.
In a dull first half, Brechin went close on 43 minutes when David McKenna's header hit the post.
With Forfar creating more after the break, they were rewarded on the hour when Martyn Fotheringham's corner fell for Templeman to fire home.
Brechin were reduced to 10 men when substitute Derek Carcary lashed out after a Chris Hegarty challenge.
Nelson, McClune, McLauchlan, McLean, Dunlop, Fusco, Brady (David Crawford 67), Molloy, McKenna, McManus (Lister 46), King (Carcary 46). Subs Not Used: Scott, Janczyk.
McHugh, Ross, McCulloch, Shaughnessy, Tulloch, Byers, Mowat, Fotheringham (Gibson 74), Low, Templeman (Wilson 80), Crawford (Hegarty 74). Subs Not Used: Paterson, Bolocheweckyj.