Australian Minister of Foreign Affairs confirmed the release of "an Australian kidnapped in Yemen," without naming him.
Oman's foreign ministry did not name the man and it was not immediately clear if he was Craig McAllister, who was abducted in the rebel-held Yemeni capital Sanaa in September.
The ministry said only that it had acted at the request of the Australian authorities.
Australian Minister of Foreign Affairs Julie Bishop confirmed the release of "an Australian kidnapped in Yemen," without naming him.
"The Government will not be making any further comment on this case in order to protect other Australians who remain captive overseas or face the risk of kidnapping. The family has asked for privacy, and I ask others to respect their wishes," Bishop said in a statement.
Bishop thanked Sultan Qaboos for "Oman's work to locate and receive the Australian national in to Oman."
Oman is the only Gulf Arab state that is not part of a Saudi-led coalition that has been battling the Yemeni rebels since March 2015.
It has mediated the release of several Westerners, including an American in November.
McAllister appeared in a 12-second video in January urging his government to meet the demands of his unidentified kidnappers.
In a similar video released in October he said he had been working in Yemen as a football coach and that his captors were seeking money.
The Shiite Huthi rebels overran Sanaa in September 2014, forcing President Abedrabbo Mansour Hadi and his government to flee the capital.
Dozens of foreigners have been taken hostage in Yemen over the past two decades, mostly by tribesmen as bargaining chips to secure concessions from the government.
Almost all have been freed unharmed.
But more recently Al-Qaeda's powerful Yemen branch has abducted a number of Westerners.
In December 2014, US journalist Luke Somers and South African teacher Pierre Korkie died during a failed attempt by US commandos to rescue them from an Al-Qaeda hideout.