The 33-year-old's lawyer, Peter S. Christiansen, told BBC Sport it was a "very standard request".
The Wall Street Journal says the warrant was recently sent to the court system in Italy.
Ronaldo denies assaulting Kathryn Mayorga at a Las Vegas hotel in 2009.
"Mr Ronaldo has always maintained, as he does today, that what occurred in Las Vegas in 2009 was consensual in nature, so it is not surprising that DNA would be present, nor that the police would make this very standard request as part of their investigation," said Christiansen's statement.
German weekly news magazine Der Spiegel, which first published the story about the allegation in October, said Ms Mayorga filed a report with Las Vegas police shortly after the alleged incident.
Der Spiegel said that in 2010, she reportedly reached an out-of-court settlement with Ronaldo involving a $375,000 (£288,000) payment for agreeing never to go public with the allegations.
Her lawyers are now seeking to declare the non-disclosure agreement void.
Ronaldo's lawyer has previously said his client does not deny entering an agreement but that "the reasons that led him to do so are at least to be distorted".
He added: "This agreement is by no means a confession of guilt."
Ms Mayorga was inspired to speak out by the #MeToo movement, her lawyer has said, and is suing Ronaldo in a lawsuit in the United States.
Ronaldo moved to Juventus from Real Madrid for £99.2m in July. He has won the Ballon d'Or - awarded to the world's best footballer - in 2008, 2013, 2014, 2016 and 2017.
The Portuguese international has previously dismissed the allegation as "fake news" and earlier in October issued a statement through his Twitter account in which he "firmly" denied the accusation.
His lawyers claim documents used in Der Spiegel's investigation have been "completely fabricated" but the publication says it has "no reason" to doubt the authenticity of key documents used in its story.