"Our wedding was beyond magical," van Amstel told ET on Wednesday. "We couldn't have been more blessed having all our friends help us."
According to the 44-year-old dancer's rep, 137 guests attended the wedding, including van Amstel's former DWTS partners, Kelly Osbourne (season nine) and Sabrina Bryan (season 15), as well as fellow pros Chelsie Hightower and Ashly DelGrosso. His best friend, Dawson's Creek star Mary-Margaret Humes, served as best man.
"Our winter wonderland wedding in the mountains at Robert Redford's Sundance Resort was the most beautiful and romantic!" added van Amstel.
Following the reception, the newlywed took to Instagram to share highlights from his and Lancaster's special day.
"Last night surrounded by our closest friends and family, my partner Josh and I got married," van Amstel wrote alongside a snap captured from their first dance. "It turned out perfectly and I want to thank everyone who attended and all of you for your kind notes, comments, Tweets and posts. My heart is full!"