The actor, who plays Jamie Fraser in the time-travel fantasy show, said he could have imagine how much global reach it would have when he auditioned for the part six years ago.
Heughan was speaking after Diana Gabaldon, the author of the series of books which Sony and Starz turned into a hit series, was honoured for services to Scottish tourism in recognition of the impact of her stories and characters.
New research has revealed that historic sites and locations deployed by the production, which is based in Cumbernauld, Lanarkshire, have seen visitor numbers soar by more than two thirds since it went on air in 2014.
Heughan has agreed to promote a special event for tourism businesses to help capitalise on the "Outlander Effect," which will be held as part of the ExpoNorth creative industries conference in Inverness in July.
He said: "Outlander has not just changed my life completely, it’s hugely affected Scotland too, seeing our culture and heritage reach internationally and celebrated around the world.
"I first met my character Jamie Fraser six years ago when asked to audition for the TV adaptation. Little did I realise how popular and widely read Diana’s books are, or I may have been more nervous.
"I’ve seen thousands of fans each year, travel to Scotland, visit our locations and try to immerse themselves in our world in any way possible.
“They have helped fund numerous Charity projects, fitness programs, musicians, Gaelic language courses, film funding, community gatherings, even building restoration.
"I’ve seen a film studio flourish in the centre of Scotland, complete with workshops, several sound stages, edit suites and an impressive costuming department, employing huge numbers of local staff and benefiting local businesses.
"I think we grossly underestimate how much influence and enterprise Diana Gabaldon has brought to us, placing the spotlight on our country and celebrating our culture. Not only that, she has written some devilishly good characters and really enthralling books."