"He said YES!! Love this man," Bass said in an online message Sunday, alongside a photo of the pair showing off a new ring on Turchin's finger.
People.com said Bass proposed to Turchin in New Orleans where they were spending the holiday weekend.
The news came one week after Bass and his fellow former 'NSYNC members performed on the MTV Video Music Awards show in New York. The reunion marked the first time the former boy band stars shared a stage since 2002.