The glamour girl, 32, met the Latino hunk while partying in Los Angeles at Elton John’s post-Oscars bash.
According to The Sun, Katie enjoyed a sneaky kiss with a mystery man outside the party before speeding off in a cab with him.
Onlookers were left guessing as to who the relative unknown might be but Katie revealed his identity on Twitter the next day, posting a snap of the pair in a car together.
Leandro, 24, is from Buenos Aires and has starred in ad campaigns for Louis Vuitton and Coca-Cola.
Katie is rumoured to be in the US signing a deal with film studio Paramount to produce a biopic of her life.
The model posted a message on Twitter saying: “On my way to signing an exciting deal wooo,” immediately setting tongues wagging.
Katie’s divorce from cage fighter Alex is due to be finalised any day now.