The Welsh derby appeared to be sewn up for Wrexham as they took the lead in the third minute through Kieffer Moore, who scored his first goal since February and ended his run of 11 Wrexham games without scoring. Moore continued his habit of scoring against his former employers, netting his seventh goal against Cardiff.
Cardiff's defensive resources had been stretched by injuries to Calum Chambers, Dylan Lawlor, and Will Fish, forcing the new-look partnership of Joel Bagan and Gabriel Osho to be exposed immediately after clearing a Lewis O'Brien free-kick. Wrexham had 18 goal attempts to 11 and should have put the game beyond the hosts back at this level after a season in League One.
The turning point came when George Dobson brought down Joel Colwill on the edge of the box, allowing his brother Rubin to lash a brilliant free-kick over the wall and past Anthony Patterson in the Wrexham goal. Colwill's strike cancelled out Moore's early effort, denying Wrexham their first win in the Welsh capital since 1992.
Cardiff will look to build on this point as they face their next Championship challenge.