The company was founded in 1859 in Auckland and in a nation where almost every building was wooden New Zealand Insurance expanded quickly.

In the 1870s it opened offices in the United States and in the 1880s created agencies in Asian countries.

[2] In 1981, NZI merged with South British Insurance; the two companies had been equally matched rivals and were virtually the same size, but with different emphasis on the types of business they held.

The new company formed a parent, New Zealand South British Group Ltd, which maintained both brands concurrently before changing to the NZI Corporation in 1984 when the South British brand was phased out.

NZI focuses on providing products to the intermediated market, i.e. brokers and banks.