Luke Jones' late goal saw Kidderminster leapfrog Southport and into the Blue Square Bet Premier play-off places.
Alan Moogan fired in left-footed for the Sandgrounders, before Anthony Malbon equalised after latching onto Lee Vaughan's pass.
Harriers keeper Tony Breeden took centre stage after the break as he kept the hosts at bay with some fine saves.
Jones struck the decisive goal in the last minute after being set up by substitute Mickey Demetriou.
VIEWS FROM THE DRESSING ROOM:
Kidderminster manager Steve Burr told BBC Hereford and Worcester:
"We knew what to expect from Southport - we knew they would keep putting us under pressure with long throws and long balls down the middle.
"I thought Luke Jones, [Tom] Marshall and the rest of the back four coped with that very well.
"That was something we had been working on this week as we knew what to expect from them.
"It was a great finish [from Anthony Malbon] although I thought he should have scored a little earlier when he had a good opportunity that was blocked, but he has done fantastically and his goal was class."