This hotel on the Havre des Pas seafront was built in the late 1880s as two private houses, followed soon afterwards by two more, creating a terrace which was numbered Ommaroo 1-4. The name derives from New Zealand, where a town named Oamaru was named after a Maori chieftain. The architectural style is typical of that found in New Zealand and Australia in the second half of the 19th century, with verandahs with delicate cast iron work.
By 1898 the first two houses in the terrace had been converted into lodging houses to take advantage of the increase in business in the area brought about by the opening of the sea water bathing pool. In 1916 the four houses were combined to create a hotel, which was sold in 1922 by John Sinnatt, an undertaker who lived at Chateau de la Mer opposite.
The curved conservatory entrance and new wing on the right of the hotel were built late in the 20th century. Behind the hotel is the original coach house, a granite building with brick window trim, now used as the laundry.