The action comes after the magazine ran an interview with So Solid Crew star MC Harvey, in which he spoke about an alleged relationship with the Girls Aloud singer.
Cole strongly denied the claims on Twitter last week, asking the rapper: "Was this 'relationship' happening in your head @harveyofficial?! Are you smoking something ? I think I've met you once maybe twice at public events and With your wife !! #s**tjustgetsweirder"
However, in a radio interview, Harvey has insisted that he never suggested he had had a sexual relationship with Cole, instead describing it as a "communication relationship" due to the emails he had received from her.
A statement from Cole's representatives said: "Cheryl Cole has today commenced legal proceedings in London against the publishers of Now magazine as a result of its two articles about her alleged "secret romance" with Michael Harvey.
"Cheryl's lawyers have asked to see Mr Harvey's alleged e-mails which the magazine says are "proof" of the "romance" but it claims not to have them in its possession. Mr Harvey's claims are denied by Cheryl and she looks forward to seeing both him and the magazine in Court at the very earliest opportunity."
Now has continued to defend the interview, with Tim Parish - a media lawyer and legal advisor to the magazine - verifying the existence of emails between Cole and Harvey.
"I concluded that the messages were real, had not been doctored in any way and confirm he was in a romantic relationship with the sender," he said in a statement.
> Cheryl Cole, MC Harvey: Now magazine stands by story
Watch MC Harvey discuss Cheryl Cole below: