In May 2014, Ssewankambo was called up to the Sweden U21 squad for the first time. He made his debut for the U21 national team, coming on as an 81st-minute substitute, in a 2–0 win against Sweden U21 on 4 June 2014. Three months later on 9 September 2014, Ssewankambo made his first start for Sweden U21 and played the whole game, in a 4–3 win against Turkey U21. In a follow–up match, he made another start for the U21 national team and played 73 minutes before being substituted, in a 2–0 loss against France U21. In a return leg, Ssewankambo was placed on the substitute bench, as the U21 national team managed to overcome the deficit by beating them 4–1 to qualify for the UEFA European Under-21 Championship. He made two appearances for Sweden U21 between 11 June 2015 and 16 June 2015 against Denmark U21 and Albania U21. However, Ssewankambo did not make the cut the U21 national team squad for the UEFA European Under-21 Championship. After spending almost a year away from the U21 national team, he made his first appearance for Sweden U21, starting a match against Serbia U21 on 24 March 2017, but suffered an injury that saw him substituted in the 10th minute. In May 2017, Ssewankambo was called up to the Sweden U21 squad for the UEFA European Under-21 Championship. However, he appeared three times as an unused substitute, as Sweden U21 were eliminated in the Group Stage tournament. Following this, Ssewankambo became a regular for the U21 national team, making ten consecutive starts between September 2017 and October 2018. During which, he scored his first Sweden U21 goal, in a 3–0 win against Malta U21 on 10 October 2017. However in a match against Belgium U21 on 16 October 2018, Ssewankambo was sent–off in the 41st minute for a straight red card, in a 3–0 loss, in what turns out to be his last appearance for the U21 national team. Following this, he went on to make twenty–one appearances and scoring once for Sweden U21.