The 36-year-old Ukrainian-American and 29-year-old New Zealand-born professional dancers celebrated at a masquerade-themed party at the Diamond Horseshoe club in the Paramount Hotel.
"I'm obsessed with the amount of love in this room. I'm so thankful for everyone that created these memories with us. Thank you @diamondhorseshoenyc," Murgatroyd wrote on Instagram.
"Officially the best day of my adult life! Worlds collided and love flooded the room! Thank you to @ldvlife for putting on an event of a lifetime and to @diamondhorsehoenyc," Chmerkovskiy added.
Chmerkovskiy and Murgatroyd danced as pros on ABC reality competition Dancing with the Stars and got engaged in December. The couple was joined by other Dancing pros, including Chmerkovskiy's brother Val and Sharna Burgess, and Val's Season 20 partner, Rumer Willis.
"Hugs and endless love for the most beautiful girl in the room, inside and out, every time. What an incredible night baby girl, and it's just the beginning of a new incredible chapter in your life. Love you beyond @petamurgatroyd #bestengagementpartyever," Burgess wrote.
Chmerkovskiy and Murgatroyd met during a Broadway production of Burn the Floor in 2009 and first appeared together on Dancing in 2011. The two previously celebrated their engagement with a tropical getaway to Saint Martin for New Year's.
"I'm not sure how 2016 can top this incredible year... but it's an amazing feeling knowing the best is yet to come baby @maksimc #StMaarten #grateful #lifeisgood," Murgatroyd wrote at the time.
Chmerkovskiy competed on Seasons 2 through 5 and 7-15 of Dancing, and won Season 18 with Meryl Davis in 2014. Murgatroyd joined Dancing in Season 13, and was forced to sit out Season 21 due to injury.