The man travelled to the Nigerien capital of Niamey from the Ghanaian capital Accra, passing through Abidjan in Ivory Coast and Ouagadougou in Burkina Faso, the Health Ministry said in a statement read on national television late on Thursday.
Out of those four countries, only Niger had not yet had its first COVID-19 case. The patient is in stable condition, according to the ministry.
Niger is the 36th among Africa’s 54 countries to have a confirmed case.
The continent had been largely spared from the pandemic for weeks, but has now recorded more than 700 cases and at least 17 deaths, according to the World Health Organisation.
There are concerns that weak national health systems in Africa will be quickly overwhelmed by the outbreak.