The New Zealand Herald understands the 32-year-old has been seeing Black Sticks midfielder Gemma Flynn for at least six months. It is also understood the couple spent Christmas together.
McCaw did not return calls. His agent Dean Hegan - who is also agent to All Black teammate Dan Carter - could not confirm details.
He said he doubted McCaw would speak about anything to do with a relationship.
Mr Hegan said McCaw was in Auckland fulfilling requirements for an advertisement.
Flynn, 22, is a student at Massey University and is studying towards a bachelor's degree in sports science.
She is originally from Tauranga but is living in Auckland.
Her mother, Michelle, laughed and politely declined to comment when the Herald called.
Flynn is regarded as one of the country's top players.
She was in the team that went to the London Olympics last year and also played at the 2008 Beijing Olympic Games.
Flynn was named yesterday in the Black Sticks squad for the five-test series against Argentina starting on February 24.
McCaw told Radio Live in April: "There's actually no one at the moment - I'm still on the lookout."
Past girlfriends have included broadcaster Nicola Grigg and sports presenter and dancer Hayley Holt.
- Vaimoana Tapaleao of the New Zealand Herald
