Mulenga progressed through several national Zambian youth teams and was called up to the senior team in a match against Sudan in May 2004, at the age of twenty, because of his good performances in the second division of Zambia. In the 2006 FIFA World Cup qualifiers, he scored against Togo in the first match of the group stage. However, the third place in the standings was not enough for Zambia to qualify for the World Cup. The country did however manage to qualify for the 2006 Africa Cup of Nations at the expense of the DR Congo and Mali. Due to an injury, Mulenga did receive any caps during this tournament, but two years later he was part of the team's starting eleven during the 2008 Africa Cup of Nations, and scored the 2–0 goal in a 3–0 win over Sudan. Zambia did not advance from the group stage in this tournament. Mulenga also had to cancel due to an injury for the 2012 Africa Cup of Nations.