The couple issued a joint statement Thursday, saying: "We're excited and incredibly happy about our engagement and we look forward to a wonderful future together."
People.com reports that Lachey proposed to Minnillo on a beach in California Thursday. Lachey then took to his Twitter page to celebrate the good news. "Hey all. If anyone's heard the rumors of my engagement, they are absolutely true! Vanessa and I couldn't be happier. Thanks for all the love."
The couple have been dating since 2006 and briefly split apart in 2009.
Lachey was previously married to pop star Jessica Simpson. The couple were stars of the popular MTV reality show, "Newlyweds."
Lachey is currently a host of NBC's "The Sing-Off" and Minnillo is host of ABC's "True Beauty."
"The Sing-Off" premieres its second season December 6 on Little Rock's KARK Channel 4.