He has now turned his incredible likeness of British actor Kit Harington – who plays the pivotal part – into a part-time profession, with him taking part in events all over Italy and Europe.
The fine arts student says it all started over a year ago, while he was still unfamiliar with Game of Thrones and 'hundreds' of people told him he should check the show out.
Giammarco said: "Some people genuinely believe I am Kit Harrington.
"Especially when I visit big touristy cities like Rome or Venice, people go crazy and think that I am Kit pranking them by speaking Italian."
Giammarco, a painter and aspiring actor, says his resemblance to Jon Snow has now become such a big part of his life that he can't help but feel personally involved when he watches the show.
"I believe Game of Thrones to be the greatest masterpiece of the small screen, and for me it has become a lifestyle.
"I am personally loving this last season, in spite of all the bad reviews it's had so far, there have been a couple of episodes that were just great pieces of art.
"I am not too worried by the fact the show is over, I look like Kit in and out of costume, so I am sure I will be able to impersonate his future characters as well."