The 19-year-old is yet to play for the country of his birth after only committing himself last month.
But boss Marc Wilmots has included the attacker as one of 12 Premier League players in an initial 24-man party.
The others are Januzaj's United team-mate Marouane Fellaini, Manchester City's Vincent Kompany, Chelsea trio Eden Hazard, Romelu Lukaku and Thibaut Courtois - the last two have been on loan at Everton and Atletico Madrid - Tottenham's Mousa Dembele, Nacer Chadli and Jan Vertonghen, Everton's Kevin Mirallas, Arsenal's Thomas Vermaelen and Liverpool's Simon Mignolet.
Aston Villa striker Christian Benteke has been ruled out by injury, with 19-year-old Lille striker Divock Origi called up in his place.
Club Brugge's experienced midfielder Timmy Simons, who is approaching 100 caps, is the most notable exclusion.
Wilmots has included Silvio Proto as a fourth goalkeeper because of injury doubts over Koen Casteels. One of the pair will be cut from the final squad.
Belgium are in Group H along with Fabio Capello's Russia, South Korea and Algeria.
Goalkeepers: Thibaut Courtois (Chelsea), Simon Mignolet (Liverpool), Koen Casteels (Hoffenheim), Silvio Proto (Anderlecht)
Defenders: Toby Alderweireld (Atletico Madrid), Anthony Vanden Borre (Anderlecht), Laurent Ciman (Standard Liege), Jan Vertonghen (Tottenham), Vincent Kompany (Manchester City), Daniel Van Buyten (Bayern Munich), Thomas Vermaelen (Arsenal), Nicolas Lombaerts (Zenit St Petersburg)
Midfielders: Axel Witsel (Zenit St Petersburg), Steven Defour, Marouane Fellaini (Manchester United), Nacer Chadli (Tottenham), Moussa Dembele (Tottenham), Kevin De Bruyne (Wolfsburg), Adnan Januzaj (Manchester United), Eden Hazard (Chelsea)
Forwards: Dries Mertens (Napoli), Kevin Mirallas (Everton), Romelu Lukaku (Chelsea), Divock Origi (Lille)
Standby: Sebastien Pocognoli (Hannover), Radja Nainggolan (Cagliari), Thorgan Hazard (Chelsea), Jelle Van Damme (Standard Liege), Guillaume Gillet (Anderlecht), Michy Batshuayi (Standard Liege)
I'm gutted he didn't choose Ireland. I presume we were eligible, he could have played for everyone apart from Peru from what I remember?- bale doubt