A total of 3,939 red and white clad people gathered in front of the parliament building in Bucharest. Watched by a representative of Guinness World Records, they paraded through the city handing out gifts.
Romania hopes to break other records after Christmas, including the world's largest sausage and the longest cake.
"It's Christmas spirit, we're all better and more generous this time of year," the Bucharest Herald quoted Mayor Sorin Oprescu as saying.
Speaking as the volunteers donned their outfits, Guinness representative Lucia Sinigagliesi said the minimum requirement for the record to be judged was a "very challenging" 3,000.
"We never know what really is going to happen with mass participation records but it looks very good."
"There are a lot of people already, so we are hoping for the best," she said.
When the record was confirmed, Ms Sinigagliesi presented a certificate to the mayor, to delight of the massed Santas.
The event easily broke a previous record of 3,618 simultaneously gift-giving Santas, set in Taiwan, in 2003.
New Santa Claus Guinness World Records 2008 set in Romania Video
