The previous time the pair clashed at this level of competition was in 1999, when Cardiff and Swansea were last in the same division.
Typically of the football fates, supporters of both sides now have a third exciting Welsh derby to look forward to this season.
"It's one of those inevitable draws and some rehearsal for 30 November," Cardiff chairman Peter Ridsdale told BBC Sport Wales.
"It'll make many mouths water and I don't think there will be many spare tickets!
"Even leaving aside the third round of the Cup it'll be about bragging rights, but we've just got to get on with it and win.
It's a fantastic draw and we look forward to a great night for Welsh football
Swansea chairman Huw Jenkins
"I've heard a lot about Swansea v Cardiff and been involved in a few emotional derbies myself, like Leeds v Manchester United.
"Our job will be to focus on the football and take the emotion out of it.
"But the first thing is to speak to Swansea and to the police, sort out Cardiff's ticket allocation, and - most importantly - to ensure a safe environment for everyone."
Swansea chairman Huw Jenkins insisted that concerns over security should not dominate the fixture.
"Football has moved on and both of these clubs have moved on from some of the things that have gone on in the past," he told BBC Sport Wales.
"We're at the Liberty Stadium and Cardiff are looking forward to moving to their new ground, there are a lot more women and children coming to games.
"We can be positive, it's a fantastic draw and we look forward to a great night for Welsh football."
Swansea earned the right to play in the third round of the tournament by beating Premiership new boys Hull City 2-1 after extra time in Tuesday night's second-round match.
Cardiff had a slightly more comfortable ride, seeing off League One side MK Dons by the same score over a regulation 90 minutes.
In the rest of the third-round draw, holders Tottenham will visit Newcastle as they start their defence of the Carling Cup.
There are three more all-Premiership ties, with Chelsea visiting Portsmouth, Manchester United hosting Middlesbrough and Blackburn having home advantage over Everton.
Full draw for Carling Cup third round:
Arsenal v Sheff Utd Brighton or Man City v Derby Burnley v Fulham Portsmouth v Chelsea Blackburn v Everton Rotherham v Southampton Swansea v Cardiff Ipswich v Wigan Stoke v Reading Leeds v Hartlepool Watford v West Ham Man Utd v Middlesbrough Liverpool v Crewe Aston Villa v QPR Sunderland v Northampton Newcastle v Tottenham
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