The celebrity chef and his partner Michelle welcomed little Valentino just eight weeks ago and they've revealed they found a lump growing on his neck.
The parents were told he is suffering from Neuroblastoma cancer and is undergoing treatment in hospital, according to Hello! Magazine.
A spokesperson for the star said: "Jean-Christophe's priority at this time is supporting his family as they deal with this devastating news, it is still very early days but they remain positive and believe the NHS experts are doing everything possible.
"Jean has had to postpone all his immediate work over the next two weeks to be with his baby and support his family but is grateful for the understanding and support during this very difficult time."
Less than 100 children in the UK are diagnosed with the type of cancer each year, and most of them are under five.