Authorities said Sam Bracanov, 74, was arrested after video surveillance footage allegedly showed him in downtown Auckland preparing to commit an assault, ONE News reported.
ONE News reported Bracanov allegedly had an item with him, but authorities declined to say what the item was.
He was to appear in court Tuesday, TVNZ said.
Police said other protesters were in with the crowd gathered to catch a glimpse of the royal couple.
"Go home and don't come back," protester Kerry Bevin yelled as the couple passed.