This will be the first marriage for Minnillo, 29, and the second to 36-year-old Lachey who was married to Jessica Simpson from 2002-2006.
Minnillo said they have no plans to do a reality show a la MTV’s Newlyweds: Nick and Jessica, which caused strain in Lachey’s relationship with Simpson, 30.
Lachey proposed with a platinum, asscher cut diamond ring with trapezoids on the side from Bader & Garrin, which Minnillo was wearing while being photographed in Mexico.
The two stars made the announcement on Thursday to US Weekly Magazine.
No word on when they will be newlyweds.