"I have received official confirmation that Adnan Januzaj has made himself available to the Belgium national team for the rest of his career," Wilmots said on his Twitter feed.
Januzaj - who is also eligible for Kosovo, Albania and Serbia and was linked with an eventual switch to England - could now be selected for the World Cup finals in Brazil this summer.
The 19-year-old, born in Belgium to Kosovan parents, has been in England since he was 16 but was reportedly being encouraged by his Albanian-Kosovar father to play for Kosovo.
Serbia - and Croatia and Turkey, who were also named as possible national teams - was never a realistic option for Januzaj though.
And it seems he has opted for the land of his birth, with coach Wilmots tweeting the news in French and Flemish.
Januzaj has scored four goals in 24 league appearances since making his debut in the Community Shield in August.
Belgium are widely tipped to have a successful World Cup with many bookies installing them as fifth favourites after they cruised their qualifying group, picking up 26 points from a possible 30.
They were drawn alongside Algeria, Russia and South Korea in Group H for the Brazil tournament.
Wilmots is expected to announce his initial squad on May 13.
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- Adnan Januzaj
- Belgium national team