The National Enquirer recently reported the couple "sat in stone silence" after "what appeared to be an argument" during a night out at a Los Angeles restaurant last month.
But Lachey's representative told Usmagazine.com the account is "not true."
"They are 100 percent together and fine and in love," another source told Usmagazine.com. "Nick and Vanessa did go to dinner that night but there was no fight. When they got in the car, Vanessa looked annoyed in pictures because she was fixing her eyelash!"
The insider said the couple took a "romantic trip" to New York last weekend.