HMNZS Canterbury left Wellington Harbour first thing Monday morning loaded with supplies for Christchurch.
The crew of the Royal New Zealand Navy frigate spent the night loading, with many of them working for more than 24 hours.
The Canterbury is due to arrive in Lyttelton at 7pm, though unloading won't start until about midnight.
That's because the ship's slightly delayed departure - after arriving from Lyttelton on Sunday night it first had to unload equipment for the army exercise it had been involved in - means it has missed the window for ideal tidal conditions for unloading.
The Canterbury is carrying fuel, much needed food, water, and medical supplies and several vehicles, including a fire engine.