Senegal's health minister, Awa Marie Coll Seck, said the patient was a man from Guinea. He had visited a hospital in Dakar on Tuesday but concealed that he had had close contact with Ebola victims in his home country.
The case marks the first in time a new country has been hit by the outbreak since July, and comes a day after the World Health Organisation warned the number of infections was increasing rapidly.
Scientists meanwhile said the first human trials of a potential vaccine would start next week using a product made by pharmaceuticals giant GlaxoSmithKline and the US government.
The experimental drug, ZMapp, had proven 100 percent effective in tests on primates, according to an article published in the journal Nature on Friday.
ZMapp is a mix of three antibodies that help the immune system destroy the Ebola virus, Reuters reported.
In the study, scientists led by Gary Kobinger of the Public Health Agency of Canada tested a group of infected monkeys and left a control group untreated.
All three untreated monkeys died of Ebola by day eight of the trial.
For those on ZMapp, even advanced symptoms such as rashes, liver dysfunction and haemorrhaging disappeared, a result Kobinger called "beyond my own expectations".
Two US aid workers treated with ZMapp have recovered from Ebola. However, doctors do not know if it aided their recovery, and a Liberian doctor and a Spanish missionary died despite treatment with the drug.
The Ebola outbreak in West Africa has killed 1,552 people out of 3,069 confirmed cases, the World Health Organisation said. The agency said the disease could eventually infect up to 20,000 people.