Authorities say he is stable with no serious symptoms and is being treated at a hospital in Lagos.
The Nigerian government said it had prepared for this eventuality and had activated its national emergency operations centre to implement control measures.
The authorities have started identifying all those who may have come into contact with the patient since his return to Nigeria.
More than 80,000 people are now known to be infected in 40 countries. More than 60 people are known to have died outside China, where the outbreak began. However, the number of infections reported within mainland China continues to fall.
Elsewhere on the African continent, Algeria and Egypt have also confirmed cases of the disease.