The former 98 Degrees singer and the TV host-and-model - who tied the knot in front of just 35 friends and family in an intimate Caribbean ceremony on Necker Island earlier this month - decided to pen their own pre-nuptial promises to each other to ensure the words were "more meaningful" to them than the traditional vows.
He explained: "We decided to write our own wedding vows for the ceremony because it makes it more personal and more meaningful when the words you're saying to each other come from your heart."
The 30-year-old 'True Beauty' host revealed her personalised vows were important to her because she knows no other bride will ever repeat those words.
Speaking in the 'Nick & Vanessa's Dream Wedding' TV show, she said: "It's something really special knowing that these vows that I write to him and that he writes to me will never be said by anybody else because these are my words from my heart and my soul that I'm giving to him and him to me."
The couple recently returned from a 10-day honeymoon to the French Caribbean island of St. Barts, but Vanessa insisted she did not mind where they spent their post-wedding holiday as long as she was with her husband.
She added: "Regardless of where we go I know we'll be going there as Mr. and Mrs. Lachey and I'm really excited about that."