Awa Marie Coll Seck told reporters on Friday that a young man from Guinea had travelled to Senegal despite having been infected with the virus.
The man was immediately placed in quarantine, she added.
The current outbreak, which began in Guinea, has killed more than 1,500 people across the region.
At least 3,000 people have been infected with the virus. The World Health Organization (WHO) has warned it could get much worse and infect more than 20,000 people.