William Edjenguele's late header handed the League Two strugglers the win after Tom Soares had equalised Anthony Stewart's 16th-minute opener for the hosts.
Matt Bloomfield was sent off 14 minutes from time for the Chairboys but it didn't detract from the much-needed victory for Jepson, who was given a deal until the new year on Friday.
"It was a good victory," said Jepson, who replaced Kevin Blackwell earlier this month. "It was a shame to go 1-0 down from a set-piece. In the first half we were a little bit scrappy but we were still making headway.
"At half-time there were a few words said and I got a fantastic response from the boys. Even before they were down to 10 men we were at it and our tails were up and thankfully we got a couple of goals today.
"The chairman has asked me to take over until January. I'll do that and once I'm here I will give it my all. If it's successful and then come January he thinks I'm the man for the job, then fine - if he doesn't, I'll shake his hand.
"I'm not one of those people who shouts: 'give me the job'. You get judged on results. My appointment gives the club stability and that's the decision the board made."
Stewart gave Wycombe the lead from a corner, meeting Josh Scowen's cross at the far post to volley into the top corner.
But Soares grabbed a deserved equaliser for the visitors on 69 minutes when he finished Anton Forrester's clever cut-back.
Bloomfield was sent off for a rash challenge on Shaun Beeley before Edjenguele climbed highest to head home Chris Sedgwick's corner two minutes from time.