Nyusi and his wife took rapid tests and were asymptomatic but immediately decided to isolate while awaiting their PCR results, the presidency statement said.
Mozambique's coronavirus infections are at their peak, data from a Reuters tracker show, with the average number of new cases increasing for seven days in a row.
In total, it has recorded over 2,000 COVID-19 related deaths and 192,000 infections during the pandemic.
Impoverished Mozambique is grappling with a debt crisis and an Islamist insurgency as well as COVID-19.
The discovery of massive natural gas reserves saw Mozambique emerge as a potential major fuel exporter, but graft scandals and the insurgency have undermined that.
(Reporting by Manuel Mucari; Editing by Alexander Winning and Andrew Cawthorne)
