Students turned out enmasse to vote with the count taking almost 24 hours after casting votes started on Friday at 06:00 hours and ran into Saturday.
The stakes were high with the two leading candidates going neck and neck amidst allegations of political parties throwing their weight behind some candidates.
Hamusanga who is a third year student in the school of Humanities and Social Sciences emerged winner polling 1,760 ahead of his closest rival Andrew Mwansa who managed 1, 173 votes.
In distant third was Jack Banda who got 174 votes.
The University of Zambia has had no student union for two years after Higher Education Minister Nkanda Luo banned unionism following student protests.
The new UNZASU president Hamusanga had students rallying behind him under the slogan “Wallah” while Mwansa had the “Tamanga” brand as his slogan.