When British explorer James Cook came searching for a southern continent, it was both New Zealand and New South Wales that he mapped in 1769–1770. This initial journey was followed rapidly by British colonization of six Australian colonies and New Zealand. One hundred years later, intercolonial conferences were held to discuss trade, defense, communications, and a federation of the Australasian colonies. Ultimately, New Zealand chose to remain independent of Australia, although the Australian Constitution of 1901 included clauses to allow for a later accession for colonies such as New Zealand. Since then, there have been ebbs and flows in the degree of cooperation and competition, and asymmetry and connectedness between the two countries. Growing differences in size and scale have been interpreted to mean the relationship has always been more important to New Zealand than Australia. However, exogenous factors have also pulled these geographically contiguous countries together in a way that often overshadows asymmetrical dependency and the inevitable tensions that arise as a result. This chapter reviews whether this argument still holds given recent divergence in approaches to immigration, human rights, and engagement with Asia.