The 66-year-old was found guilty in a Paris court of spending tens of millions of euros more on his campaign than was permitted under the law.
First started in March 2014, the criminal investigation into what has been dubbed the "Bygmalion case," discovered that Sarkozy's campaign spent more than $54 million during the campaign by using fake invoices, way above the limit of $24 million set by French electoral laws.
He will not be jailed, however, and can serve his sentence at home with an electronic bracelet, the court ruled.
Mr Sarkozy has denied any wrongdoing and is expected to appeal the ruling.
It is his second one-year prison term. In March, he became the first former president of France to receive a custodial sentence - for corruption and influence peddling - but remains free pending an appeal of that sentence.