Stags - who had beaten the same opposition three days earlier to lift the league cup - were gifted the opening goal in the sixth minute. Marcus Bedford put keeper Sheikh Ceesay under pressure and his clearance went to Lewis Hamilton who finished.
In the 22nd minute Jordan Warren’s free kick was flicked on by Harry Giles and Liam Dreckmann poked home for 2-0.
Epsom pulled a goal back in the 39th minute as Mario Qurassaca got free and his touch led to Bird being caught in no man’s land and Qurassaca headed over him from 18 yards.
Bird made a smart save from Mike Hill on the stroke of half-time.
After the break the Stags defended well to frustrate Epsom, whose best chances came from a couple of set pieces, but Bird commanded his area well.
Billy Conner looked like he’d won a Stags spot kick but it wasn’t given. But 2-1 is how it stayed.
Boss Ewen said: “It’s been a great week winning the cup then getting into the play-off final. We managed the second half well.
It was great to see a good crowd, who we thank. I’m hoping we get the same this Saturday to give us that final push.”