A 90th-minute howler from Wrexham goalkeeper Arthur Okonkwo saw Swansea hit back to win 2-1 in the first league meeting between the two Welsh sides in 22 years.
Cameron Burgess' unfortunate own goal gave Wrexham the lead early on at the Swansea.com Stadium, his third of the season at the wrong end.
Swansea hit back in the second half as Zan Vipotnik's heavily-deflected strike evaded Okonkwo in the Wrexham goal.
And then the winner came on 90 minutes as substitute Adam Idah tapped in from close range after Okonkwo spilt the ball after failing to gather it cleanly and dropped the ball at his feet.
This was the first league meeting between the two clubs since 2003 when Wrexham made the trip to Swansea's former Vetch Field home.
Much has changed since then with both clubs having risen through the divisions, Swansea spending seven years in the Premier League between 2011 and 2018 and Wrexham now back in the second tier after escaping non-league football and enjoying three successive promotions.
Wrexham were gifted the lead when Burgess sent a header flashing past his own goalkeeper Lawrence Vigouroux.
It was the defender's third own goal of the season following his unfortunate November double against former club Ipswich and Burgess looked suitably crestfallen.
Swansea hit back and the hosts' endeavour was finally rewarded by Vipotnik's willingness to shoot and a slice of luck.
It got even better for Swansea as Okonkwo went walkabout in his area and produced a howler for Idah to seal their first league win over Wrexham in 32 years.
Swansea's Vitor Matos:
"It was a derby and these games have these kind of moments. We started the game a little bit nervous and anxious, then there was the own goal.
"But more importantly than the result for us was the way we bounced back from that situation we found ourselves in.
"Adam is a striker and he has the hunger to score. He wanted to have an impact on the game and I'm really happy for him. He helped the team and the impact players can have when they come off the bench is massive."
Wrexham's Phil Parkinson:
"It's very frustrating. It's difficult to legislate for those two goals that have gone against us tonight. A double deflection for the first, and then with the second I feel for Arthur because he has been outstanding for us, not just this season but over the last few seasons.
"We do feel for him tonight, but it's one of those moments where it should never end up in the back of our net. It's a tough way to lose a game.
"We wouldn't have got to where we are without his contribution, and he's pulled off some incredible saves this season in big moments. He'll need picking up, but we'll pick him up and be ready for the Boxing Day game."
