Officers said Howard had assisted at the scene but was "not involved" in the fracas.
He is now being hailed as a hero after news of the incident did the rounds of the Liberal Party faithful.
"He took on the Taliban in his 60s and now he's taking on domestic violence at almost 80," a Liberal source said.
"He not only stopped the fight, but he stood with the woman until help arrived. Others would have turned a blind eye."
Howard, who was back walking the streets in his cricket jumper on Friday morning, declined to comment on the scuffle, but confirmed there had been "an incident".
A 44-year-old woman has been charged with breaching an Apprehended Domestic Violence Order and granted conditional bail to appear at Manly Local Court on Tuesday.
The man, aged 47, was taken to hospital as a mental health precaution.
"Police hope to speak with the man once he is deemed well enough," police said.
Howard also has a political track record for intervention to stop domestic violence. As Prime Minister in 1997, he set up a Commonwealth program called Partnerships Against Domestic Violence, pledging $50 million for research and resources over a six-year period.
Since leaving office in 2007, he has remained politically active.