More than 35,000 demonstrators poured into the harbourside city of Wellington, police said, shutting down busy streets as their spirited procession inched its way towards parliament.
Bare-chested men draped in traditional feather cloaks were joined by horse riders waving the red, white and black Maori flag.
Children marched alongside adults bearing distinctive full-face Maori “moko” tattoos and clutching ceremonial wooden weapons.
“The vibe is beautiful. People of all walks are here to support. It is peaceful and respectful,” participant Nick Stewart said.
Protests have been swelling throughout New Zealand after a minor party in the conservative coalition government drafted a bill to redefine the 1840 Treaty of Waitangi.