Sizzling Miss Scotland, 22, dazzled the judges in a sexy gold Dax bikini.
The blonde beauty was pipped by Miss Panama and Miss Gibraltar.
But speaking last night from Durban in South Africa, delighted Kat said: "I can't tell you how thrilled I am to have come third. It's a big achievement.
"To have beaten more than 100 girls from some of the world's most exotic countries is amazing. I'm having the time of my life."
Kat is in her third week in South Africa, where she's busy preparing for the Miss World finals on December 12.
She has been recording all her adventures in her weekly diary for The Scottish Sun.
And Kat is hoping to become the first Scot to win the title when the big event is held in Johannesburg.
Next week she'll compete in the Miss World Top Model contest.
Kat said: "I just hope I can win it for Scotland."