Results released by the election commission early on Tuesday morning showed Hichilema received around 60 per cent of valid votes, compared with 38 per cent for his main challenger Brian Mundubile.
It was Hichilema's seventh run for the presidency and he was widely expected to win due to the advantages of incumbency, while it was Mundubile's first bid to become head of state.
Hichilema, 64, campaigned on his economic record since taking charge during a pandemic-era debt crisis in 2021, whereas Mundubile's pitch to voters included that improving macroeconomic indicators had made little difference to their daily lives.
Copper-rich Zambia has been a focus of competition between China and the United States for its critical minerals.
After a relatively quiet run-up to the Thursday vote, tensions escalated quickly. On the night of the election, authorities arrested 11 people including leading opposition figures in a raid that involved an exchange of gunfire, while Mundubile was present.
The next day, the electoral commission suspended vote-counting for hours due to reports of violence against polling staff and the theft of ballot papers.
Mundubile said he had received information about the possible alteration of results forms from polling stations and called for an urgent independent investigation, though Hichilema's camp said he was lying.
The opposition is not expected to accept the results and could lodge a legal challenge although it is unlikely to be successful, said Greg Musiker, Zambia analyst at advisory firm Signal Risk.
"While localised political violence is possible in the coming days, widespread unrest is not expected," he added.
