Cook and Jancou were photographed together at a party hosted by skin-care CEO Peter Thomas Roth. The couple wore matching black and white outfits.
Cook and Jancou got engaged two years ago in Greece.
"We are very happy," Cook previously told People magazine.
"We consider ourselves incredibly lucky to have found, in each other, our soulmate," Cook said in a statement to Page Six at the time. "We are looking forward to many years of wedded bliss!"
Jancou will be Cook's third wife. Cook was originally married to Christie Brinkley from 1996 until 2008. The couple split up after Brinkley learned of Cook's alleged affair with his 19-year-old assistant.
Brinkley won custody of the children in the divorce settlement while Cook took home $2.1 million.
After news broke of the alleged affair with his assistant, another former employee accused Cook of having a romantic relationship with her. She was 18 years old at the time of the alleged relationship.
Cook went on to marry Suzanne Shaw. The two split up in 2014.