The 61-year-old was detained on a European arrest warrant while visiting relatives in Romania on December 29th, said the prosecutor's office in the western city of Innsbruck in Tyrol.
The suspect sparked alarm in November when he sent an anonymous email to the interior ministry, alleging he had information that a 29-year-old Syrian was in fact an Islamic State commander who was planning an attack in Innsbruck.
Acting on the tip-off, officers of Austria's elite "Cobra" force staged a major raid and arrested the Syrian on November 26th.
But they were forced to let him go 24 hours later after the Austrian admitted he had made up the whole story to stop his partner from attending an event with the Syrian.
"The motive was jealousy," Thomas Willam, a spokesman for the prosecutor's office, told AFP.
The European arrest warrant had been issued after the Austrian failed to notify police that he was leaving the country, Willam said.
Romanian authorities have yet to confirm the man's extradition.