“The man was arrested by Swedish police at (Stockholm’s) Arlanda airport as he tried to leave Sweden,” Oslo police officer Knut Jostein Saetnan said in a statement.
He gave no details about the suspect’s planned destination.
The man was not carrying the jewels belonging to King Otomfuo Osei Tutu II, but is to be extradited to Oslo on Friday.
Police told the online edition of Norwegian tabloid Verdens Gang that the suspected admitted taking part in the heist in an Oslo hotel lobby.
His nationality was not immediately known.
Police have asked the public to come forward with any information that could lead to the recovery of the jewels and pictures of them can be seen on the Internet.
Norwegian police also published CCTV pictures of a man and a woman suspected of carrying out the theft, and the suspect arrested in Stockholm had admitted he was the man shown, Verdens Gang said.
Two other suspects in the case are wanted under an international arrest warrant.
The jewels, reportedly of great value, were in a suitcase on a pile of luggage in the lobby as the Ghanaians were busy at the front desk.
King Otomfuo Osei Tutu II was in Oslo to attend a conference organised by the Norwegian-African Business Association.
The Ashanti monarch, one of Ghana’s traditional tribal leaders, is one of the country’s most revered figureheads and the government regularly consults with him.
Ghana became a republic in 1960, three years after gaining independence.