Two goals in injury-time saw Kidderminster see off 10-man Alfreton and move into the Blue Square Bet Premier play-off places.
Louis Moult was sent off just before half-time for a poor challenge on Harriers midfielder Kyle Storer.
Debutant substitute Anthony Malbon, who signed from Newcastle Town for £7,000 on Friday, put Harriers ahead by slotting home Daniel Bradley's cross.
Jamille Matt doubled the lead with a close-range finish.
Kidderminster are now fifth in the table, a point ahead of Gateshead, who drew 3-3 at home with Lincoln.
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Kidderminster assistant manager Gary Whild told BBC Hereford & Worcester:
"When they went down to 10 men we knew it was always going to be difficult.
"In the second half I thought they were brave in keeping two men up front and it was tricky for us.
"But we kept going as we have done a few times lately and eventually we got our rewards."