AFC Telford kick-started their Blue Square North promotion hopes with their first win in six matches.
Andy Brown fired the Bucks ahead from the penalty spot for only his fourth league goal of the season after home debutant Sean Evans was fouled.
Phil Trainer got the second close to the break, his shot taking a deflection to beat Alfreton keeper Paddy Gamble.
"We've had a tough time, and we needed that win very badly," boss Rob Smith told BBC Radio Shropshire.
Telford now lie 10th in the table, just six points off the play-off places and with three games in hand on two of the leading sides.
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"I tend not to look at the league table as it hasn't made pleasant reading recently," Smith added.
"But there's a lot of football to be played, and no-one's throwing in the towel from our side, that's for certain."
The defeat leaves injury-ravaged Alfreton in sixth spot, just a point outside the play-off places.
Assistant boss Russ O'Neill said: "There were a lot of positives from our display at Telford.
"Overall I thought we were the better side, we just didn't take our chances although we did gift them the lead."
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