Van Amstel, 44, tied the knot with the 27-year-old health coach in Sundance, UT, on Sunday, People reported.
"We wanted a winter wedding," van Amstel told People.
The ceremony took place outdoors in front of 137 guests.
The couple reportedly met in 2009 at a bar in Los Angeles, where van Amstel lives while shootingDancing with the Stars. They dated for four years before Lancaster moved from Austin, TX, to Utah with van Amstel.
"Sundance happens to be one of the private, romantic traditions between the two of us, so it seems only fitting to host the wedding there," Lancaster told the magazine of the location.
Not all of van Amstel's Dancing with the Stars friends could attend the ceremony due to the show's Live! tour, however, his Season 9 celebrity partner Kelly Osbourne served as the flower girl.
Van Amstel joined the cast of Dancing with the Stars way back in 2005 for Season 1. He has competed in nine seasons total, with the latest being Season 21 when he was partnered with celebrity chef Paula Deen.
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The highest the pro dancer has ever finished on the ABC series is third place.