"I'm leaving because my life is in danger. My phones are tapped," Damian Pachter, a journalist with the Buenos Aires Herald, told the website Infobae.
The website carried a photograph of Pachter, wearing a cap and carrying sunglasses, at the airport before he boarded an Aerolineas Argentinas flight.
Telam, an Argentine state-run news agency, reported that the flight was bound for neighboring Uruguay.
"I'm going to come back to this country when my sources tell me the conditions have changed. I don't think that will be during this government," Patcher told Infobae.
State prosecutor Alberto Nisman was found dead in his apartment late on Jan. 18, a gunshot wound to his head and a 22 caliber pistol by his side along with a single shell casing.
He had been scheduled to appear before Congress the following day to answer questions about his allegation that President Cristina Fernandez conspired to derail his investigation of the attack.
His death and a storm of conspiracy theories around it have rocked Argentina.
Argentina suspects rogue agents from its own intelligence services were behind Nisman's death.