The Australian and New Zealand port industries in the post-World War II period exhibit strong elements of path dependence. Simply put, economic and political actors’ purposive decisions pushed the development of port institutions down a pathway which became hard to step off: institutional lock-ins impeded strategic flexibility and the growth of port productivity; inefficient macro- and micro-level institutional arrangements reduced Australian and New Zealand port efficiency. Given this experience, our chapter uses path dependence as a method to explain institutional stability and change within New Zealand’s and Australia’s respective port systems. While port institutions in both countries were slow to adapt to shifts in the wider industry environment, they eventually succumbed to reformist change. As we explain, this occurred more strongly in New Zealand through pathbreaking institutional transformation in 1989, the pressures for which mounted over several decades. In Australia, by contrast, there were many false starts and change was slower even after the ports were caught up in the federal government’s late 1980s economy-wide programme of microeconomic reform.