The 25-year-old singer - who has son Bear, 20 months, with his former girlfriend Cheryl Tweedy, 35 - was impressed when mum-of-three Kourtney posted a racy picture of herself on Instagram wearing a sheer lace bodysuit.
Liam couldn't resist sharing his appreciation for Kourtney, 39, commenting ''Wow'' underneath the snap, which was taken behind the scenes during her cover shoot for GQ Mexico.
In the interview for the shoot, she admitted she is comfortable showing off her body.
Kourtney said: ''I am very comfortable in my own skin. I like to be naked in my house and I think it is important to show positive images of our body.''
Liam is currently single, although he had a brief romance with model Cairo Dwek following his split from Cheryl, and Kourtney is reportedly dating model Luka Sabbat, 21.
Liam and Cheryl announced in July that they had ended their two-and-a-half-year romance.
They said in a statement posted to their respective Twitter accounts: ''We are sad to announce that we are going our separate ways. It's been a tough decision for us to make. We still have so much love for each other as a family. Bear is our world and we ask that you respect his privacy as we navigate our way through this together.''
And rapper Snoop Dogg offered to take the singer to Las Vegas and help him find a new girlfriend following his separation from Cheryl.
He recently said: ''Break-ups are never easy for real, but getting angry never made anybody feel better. You know it's just going to make you feel worse.
''I like my boy Liam. He is cool. We partied a little at my album launch a couple of years back and I would like to help him out for sure.
''The best way to get over a hot woman is to go and find another hot one - well, maybe more than one!
''I can take my boy Liam to the hottest clubs in Vegas and introduce him to women so hot all his troubles are going to fade away.''
It's time for a riot grrrl revolution.
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