The man has been quarantined at the private Nyaho Clinic in the capital, Accra, health officials say.
The virus has so far killed more than 460 people since it broke out in Guinea in February and spread to neighbouring Liberia and Sierra Leone.
It is the world's deadliest outbreak to date and there is no cure for Ebola.
The US embassy in Accra said it had been informed that a US citizen was being tested but would not give any more details, Reuters news agency reports.
The man was believed to have visited Guinea and Sierra Leone in recent weeks.
Ghana's health ministry said it had put in place "precautionary measures" and people should stay calm.
Staff at the clinic had also been quarantined and provided with protective clothing, it added in a statement.
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The clinic was awaiting the results of blood tests to see whether the patient, whom the ministry did not identify, really had Ebola, the statement said.
"We will like to assure the general public that we have everything under control," Tony Goodman, the health ministry's public relations officer, said.
In April, Ghana's health authorities said a girl suspected to have Ebola had tested negative.
Ebola spreads through contact with an infected person's bodily fluids and kills up to 90% of those infected.
The health ministers of 11 West African states met in Accra last week promising to work more closely together to combat the outbreak.
So far, 759 people have been infected with the virus in Guinea, Liberia and Sierra Leone.
Most of the 467 deaths have been centred in the southern Guekedou region of Guinea, where the outbreak was first reported.
But health officials say the region's porous borders have allowed infected people to carry the disease into other countries.
A US citizen is being tested for the Ebola virus in Ghana, which has had no confirmed cases of the virus in the current West African outbreak.