The Real Madrid man's withdrawal has plunged the team into a goalkeeping crisis ahead of their friendly against the Ivory Coast in Brussels on Thursday and their two Nations League matches away against England and Iceland.
Courtois was not scheduled to be involved against the Ivorians but was expected to play against England at Wembley on Sunday, marking a return to London for the former Chelsea player.
Two of Belgium's back-up goalkeepers -- Koen Casteels and Hendrik Van Crombrugge -- have already dropped out of the squad, both to attend the birth of their children.
That has left only Simon Mignolet of the four keepers originally named in the squad.
Belgium coach Roberto Martinez has since called up Davy Roef from Gent and under-21 team goalkeeper Jens Teunckens to serve as Mignolet's deputies.