The Serbian midfielder spent a successful loan spell with the Welsh club in the second half of last season, as he made 13 appearances in the Championship to help them regain their Premier League status.
He has never managed to establish himself for his parent club Liverpool since he joined them in 2016, and so looks to be on his way out of the 'Reds'.
Cardiff boss Neil Warnock has openly praised the midfielder, and has spoken of how he would like him to join the club on a permament basis.
Grujic is with Liverpool in their preseason preparations in the USA, but has spoken of how pleased he is that the 'blue birds' are keen on his return.
"I have seen it in the newspapers and on the television, of course it means a lot to me because I was there - it means I showed some good games to them and they want me back." the 22 year-old said to 'Sky Sports'.
"But we will see what the best is for me and for the club."
The player still has three years remaining on his deal with Jurgen Klopp's team, but with the signings of Naby Kieta and Fabinho, it seems as though Grujic's chances in the first team would be even more rare than they have been so far.