Mr Biya, at 85 sub-Saharan Africa’s oldest leader, took 71.3% of the vote, according to official results.
Opposition calls for a re-run of the presidential election were rejected by the Constitutional Council last week.
Riot police were deployed on Sunday to the major cities of Yaoundé and Douala in case of opposition protests.
Cameroon’s two English-speaking provinces have been hit by more than a year of violent protests and attacks by separatist rebels which have left hundreds dead.
Two days before results were announced, Africa’s longest-serving President Teodoro Obiang Nguema of neighbouring Equatorial Guinea congratulated Mr Biya on his win.