Januzaj posted a picture with a Dortmund jersey on Twitter with the message: “Pleased to sign for Dortmund! Looking forward to new season."
The 20-year-old added on the club website: '"Borussia Dortmund are a great club, the fans here are supposed to be really incredible. I want to achieve great things with the team."
Dortmund's sporting director Michael Zorc added: “Adnan is a highly talented and technically adept player who rounds off our attack."
Good luck to @AdnanJanuzaj, who has joined Bundesliga club Borussia Dortmund on a season-long loan deal. #mufcpic.twitter.com/h5SFMovaUD
— Manchester United (@ManUtd) August 31, 2015