The 21-year-old defender has made a good start to life at Old Trafford since his summer move from Crystal Palace, starting all three of the club's Premier League matches so far and winning the Man of the Match away against Wolverhampton Wanderers.
Wan-Bissaka is joined in the England squad by Harry Maguire, Jesse Lingard and Marcus Rashford, for the Euro 2020 qualifiers against Bulgaria and Kosovo.
Although making one appearance for DR Congo at Under-20 level in 2015, the right-back has been representing England Under-21s and adds to the options available in the position for Southgate.
England face Bulgaria at Wembley on Saturday 7 September (17:00 BST kick-off) before a first meeting with Kosovo on the following Tuesday (19:45 BST start).