The model and presenter, who married Lachey in July, announced on Twitter that she had decided to drop her maiden name.
After changing her handle from @VanessaMinnillo to @VanessaLachey, the 31-year-old wrote: "So.... I'm making it official, and I LOVE my "new name"! @VanessaLachey.... has a nice ring to it ;-) (sic)."
Nick recently claimed that the couple are enjoying the routine of married life.
The former 98 Degrees singer has also said that he wants to have children with his partner "sooner rather than later".
Discussing the possibility of fatherhood back in August, he added: "I'm doing everything I can. Trust me, it would make me happy. Family is very important. It's very important to us. and I'm sure that will be around the corner."