The 18-year-old gamer, who competes as MSDossary, also collected an invitation to the world soccer body's Best FIFA Football awards in September and a gleaming new trophy.
"I'm really proud that I made my country proud," said the Saudi after winning each leg 2-0 on PlayStation and Xbox consoles while a frustrated Pinna failed to find a way through on goal.
The two men faced each other on a central stage at London's O2 Arena, separated only by their screens.
Regarded as one of the best defensive players, Aldossary also won the FUT Spring Cup in Manchester on his way to the 32-player finals.
He had one glaring missed opportunity in the first leg when one-on-one with the goalkeeper but a brace from former Brazilian World Cup star Ronaldo on the PlayStation side and then goals from Thierry Henry and Ruud Gullit in the Xbox leg settled matters.
The Grand Final, live-streamed around the world on Twitch, Twitter, YouTube, Facebook and FIFA's own platform, was the culmination of a virtual championship that started out with a global pool of 20 million entrants.