Confirming the joyous news, reps for the pair released a joint statement reading, "We're excited and incredibly happy about our engagement and we look forward to a wonderful future together."
Seemingly over the moon over the decision to spend their life together, a source tells Us magazine: "They're so happy, doing great. Thrilled about it."
As for the details, an insider dished that Lachey - who was previously married to Jessica Simpson - popped the question by bestowing Miss Minnillo with an Asscher-cut diamond with baguettes from Bader & Garrin.
Tweeting about the proposal, Lachey wrote, "I popped the question on bended knee. I do a lot of squats so my knees are very strong."