The Korean chart sensation took home two awards for his song Gangnam Style, picking up International Song of the Year and Music Video of the Year.
Meanwhile, the British boy band - who performed their hit Kiss You at the star-studded ceremony in the Palais des Festivals, Cannes, France - won the award for Best International Group.
Tweeting after taking to the stage, member Harry Styles wrote: "Thank you so much to @NRJhitmusiconly and our fans for the award!! See you later .xx."
His bandmate Niall Horan also tweeted his delight, saying: "Cannes thank your for today! We had a lot of fun! French fans thanks alot for the award! gona sit lovely beside the TV. (sic)" The group arrived at the bash shortly after Harry's ex-girlfriend Taylor Swift, who was reportedly staying in the same hotel.
The We Are Never Ever Getting Back Together - who presented an award to the best French female artist - looked stunning in a short sparkly mini-dress, amid rumours she is desperate to rekindle her relationship with the Little Things heartthrob.
The former couple were rumoured to have had a heart-to-heart in London earlier this week but have not been seen together since they broke up shortly before New Year's Eve after having an argument while on holiday in the British Virgin Islands.
Rihanna also won an award for International Female Artist of the Year, although the 24-year-old was not present at the event.
Other guests at the event included Ed Sheeran and Alicia Keys, who was accompanied by her husband Swizz Beatz. The singer celebrated her 32nd birthday on Friday (25.01.13) but is not expected to stay in France for long to enjoy an extended vacation as she is due to return to New Orleans, where she is performing the American national anthem at the Super Bowl on February 3.
Full List of 2013 NRJ Music Awards' Winners:
Francophone Breakthrough of the Year: Tal
International Breakthrough of the Year: Carly Rae Jepsen
Francophone Female Artist of the Year: Shy'm
International Female Artist of the Year: Rihanna
International Duo/Group of the Year: One Direction
International Song of the Year: Psy - Gangnam Style
Music Video of the Year: Psy - Gangnam Style