One of the men, who identified himself as a 24-year-old college student, was arrested on Sunday after climbing over a fence and dropping into a dry moat surrounding the monkey exhibit at Ichikawa City Zoo outside Tokyo, police said on Monday.
The other man, who was filming the act, identified himself as a 27-year-old singer.
Images on social media showed a person scaling the fence in a costume that included a smiley face head with sunglasses, prompting the monkeys to scatter.
The men did not go close to the animals, and were quickly apprehended by zoo officials, said an official at Ichikawa Police who spoke with AFP on a traditional condition of anonymity.
The two men face charges of forcible obstruction of business, which they refute, the police official said.
