The two gave birth to daughter Brooklyn Elisabeth on Monday, Jan. 5, Vanessa announced via her website on Tuesday.
"Nick, Camden and I are SO excited to announce the birth of our sweet, beautiful baby girl, Brooklyn Elisabeth Lachey!" the former Total Request Live host writes, also sharing a black-and-white photo of her holding her daughter's tiny hand. "I have been dreaming of this moment for as long as I can remember, the day I was going to meet my little girl."
"A friend recently told me how magical today was going to be because it’s the day I would meet my best friend," she adds. "I can’t even begin to tell you how it felt to hold her in my arms for the very first time. Mommy, Daddy and big brother Cam love you so much already, Brooklyn!"
Baby Brooklyn -- weighing 7 pounds, 15 ounces -- was born on Monday at 5:17 p.m. She joins big brother Camden John, who turned two years old in September.
Vanessa, 34, and Nick, 41, have been married since July 2011.
In November, Vanessa shared her best parenting advice with American Baby magazine, including that it's OK to not have an instant bond with your baby.
"While pregnant with my son, Camden, I felt guilty because everyone told me about this love I'd feel, and I wasn't there yet," she admitted. "I remember asking Nick, "Is something wrong with me?' I've wanted this my whole life, and I'm forcing myself to have those feelings."
Though that all changed when she found out the sex of the baby.
"For me, the love really flowed when I found out the baby was a boy," she revealed. "That's when I could finally bond, once I knew 'it' was a him."