As confirmed on Tuesday's It's All Kicking Off - Transfer Week podcast, Phillips has travelled to the Welsh capital to complete his move after spending the first half of the season on loan at Celtic.
The defender failed to gain significant minutes for the Scottish champions and was recalled earlier this month.
He follows Calvin Ramsay out of the door in loans from Liverpool this week, after the right back joined Bolton until the end of the season.
Fellow full back Owen Beck has rejoined Scottish side Dundee, where he spent the first half of the campaign until being recalled to help with an injury crisis in defence this month.
Liverpool defender Nat Phillips is set to join Cardiff City on loan after being recalled from Celtic
Phillips was not getting regular minutes at Celtic and he was duly recalled from his loan
Phillips came into the Liverpool side in 2020-21 to play a more regular role with 17 appearances in the Premier League with Virgil van Dijk sidelined with a long-term injury.
However, he was unable to keep hold of his place in the line-up, and was duly loaned out to Bournemouth in 2021-22, and after staying at Anfield in 2022-23, spent the first half of this campaign with Celtic.
He would make just eight appearances in Scotland, before being duly recalled and put up for loan elsewhere.
Mail Sport's Liverpool Confidential had previously reported that Jon Dahl Tomasson's Rovers side were best placed to land the player, despite spending money on fellow defender Connor O'Riordan from Crewe.
The emergence of Jarell Quansah has perhaps given the Reds greater cover at the back than they may have foreseen
Leeds were also keeping tabs on Phillips but Liverpool were understandably keen for guaranteed game-time after a sub-par spell at Celtic, where he failed to nail down a spot in the starting XI.
The Reds are currently without Joel Matip at the back, but the rise of Jarell Quansah this season has seen Jurgen Klopp's side bring in cover at centre back from a perhaps previously unsuspecting source.