The 37-year-old singer - who was previously wed to Jessica Simpson - threw a party with his soon-to-be wife at the London Hotel in West Hollywood, California, where the pair had a "great time" dancing with guests at a special cocktail reception.
A source told People.com: "Nick and Vanessa greeted guests hand-in-hand. Vanessa looked gorgeous in a white dress with a black sash. She and Nick both seemed very excited to celebrate with their families and friends.
"Everyone seemed to have a great time. It was a laid-back, yet sophisticated atmosphere. Guests danced until the late hours."
Nick - who proposed to Vanessa in November 2010 after four years of dating - has previously said plans for the wedding were progressing "slowly".
He said: "We're working on it. We're getting there slowly but surely. We're inching our way along."