A male, 66, was quarantined at Majuro hospital on Thursday and is identified by health authorities as a "patient under investigation", said Health Secretary Jack Niedenthal in a statement.
Mr Niedenthal also called for donor assistance to provide laboratory-testing equipment so the islands have the ability to test for the coronavirus locally.
"This case is being treated and investigations are underway, including laboratory testing, to determine if this is a confirmed case of Covid-19."
He advised the public to remain calm and practice preventative measures.