Wallace - man of the match.
Promotion hopefuls Glamorgan moved up to second place in Division Two of the NatWest Pro40 League Two after completing a comprehensive 50-run victory over Derbyshire Phantoms at Cardiff.
The Dragons, who have won five of their eight matches, will now have to sit back and wait to see if other results, notably Yorkshire final two games, go their way if they are to get into the shake-up for promotion.
The Phantoms failed dismally in their bid to chase down 206 to win, making just 155 for eight, after Jamie Dalrymple (54) and man of the match Mark Wallace (58) had helped Glamorgan, who won the toss, recover from 36 for four to make 205 for eight.
Under the floodlights and on a slow pitch Derbyshire always struggled to get anywhere near the required run rate against the seam ball bowlers, especially Jason Gillespie and Alex Wharf. And then the spinners, Robert Croft and Dean Cosker, turned the screw.
The writing was on the wall when Dan Birch was caught at point off Gillespie in the third over, before Wharf claimed the wickets of Chris Rogers - caught by Wallace from a top edge - and Wavell Hinds, who edged behind.
Eighteen-year-old Dan Redfern did his best to dig in but was trapped leg before by Croft, and in the next over Cosker took a brilliant left-handed catch to remove Greg Smith.
And any hope of Derbyshire making any sort of recovery from 73 for five ended when Tom New was stumped smartly off Croft.
But at the start of the match Derbyshire had looked in the driving seat as Glamorgan lost four wickets within the first 10 overs.
Croft only lasted until the third over before being bowled by Ian Hunter via a bottom edge, three overs later Michael Powell edged White to stand-in skipper Chris Rogers at first slip and Glamorgan's poor start was complete when Tom Maynard was smartly caught at backward point by Greg Smith.
There was more bad news for the Welsh county when captain David Hemp gloved a catch behind down the leg-side.
Dalrymple and Wright set about rebuilding the innings in patient fashion just happy to push the ones and twos. But when Wright did try an attacking shot he was caught on the mid-wicket boundary by Dan Birch off a Jake Needham long hop.
The in-form Wallace soon adopted some characteristic reverse sweeps and Dalrymple cracked Redfern for a six and a four from consecutive balls to reach a 78-ball half century. But he perished off his next ball, going leg before to Hinds.
Wallace carried on to put Hinds over the boundary for six to ensure Glamorgan past 200 before he holed out from the penultimate ball of the innings.