Imraan Hosany, editor of the weekly Sunday Times newspaper, was fined 50,000 Mauritian rupees (1,050 British pounds, 1,225 euros) for the publication of photographs that the court said were against public morality.
"The publication of these photographs were not necessary to the understanding of a public event," said court magistrate Wendy Rangan.
McAreavey, 27, a County Tyrone school teacher and the daughter of Tyrone Gaelic football boss Mickey Harte, was strangled in January 2011 and her body dumped in the bathtub of her luxury hotel room.
Mauritius, a volcanic island surrounded by coral reefs and lagoons, is best known for top-end tourism and as a honeymoon destination, with nearly one million tourists a year, employing directly or indirectly around 100,000 people.
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With tourism making up more than a quarter of the economy of the white-beach and palm-fringed island, the murder of McAreavey made headlines at home and abroad.
Last year two hotel workers were acquitted after an eight-week trial.
Police reopened investigations in July 2012, but no further announcements have made.