A man slashed the mother of his child in front of the boy as they walked in Central Park, authorities and witnesses said.
The woman was slashed on her arms and was in stable condition after the Wednesday morning attack. The alleged slasher had cuts on his wrist and was also in stable condition.
The child, 4 years old, was not hurt.
Several police officers suffered minor injuries while trying to apprehend the man. None of the injuries is life-threatening, authorities say.
Park-goers were alarmed at the midday violence.
"It's the middle of a beautiful day out on a Wednesday? That's pretty shocking, all things considered," said Joseph Ramos, of the Upper West Side.