Mr Varini, 39, won the title and a $10,000 (£6000) cash prize in the World Champion Blacksmith competition at the Calgary Stampede in Canada.
The unusual contest draws huge crowds as the most talented blacksmiths in the world compete in horse-shoeing and shoemaking against the clock.
Mr Varini saw off 65 other challengers from around the globe to became the first Scottish champion in 28 years. The father-of-one, from Dalry in Ayrshire, said: "The standard is very high and it is fast work. It's quite tricky and really close, there's not much between the top five.
"Winning it has been an ambition for a long time so I was elated and delighted."
He started working as a farrier - a specialist in equine hoof care - in 1995 after being surrounded by horses when he was growing up. He now runs Galston-based farrier business Robinson & Varini with partner and friend Paul Robinson.
David first entered the contest in 2004 and in 2008, was runner-up to Paul, who is from Northern Ireland.