Dutch Harbor lies within the city limits of Unalaska and is connected to Unalaska by a bridge. Amaknak Island is home to almost 59 percent of the city's population, although it has less than 3 percent of its land area.According to the U.S. Census Bureau, the city has a total area of 212.3 square miles (549.9 km2), of which, 111.0 square miles (287.5 km2) of it is land and 101.3 square miles (262.4 km2) of it (47.71%) is water.

As in all of the Aleutian Islands, the climate of Unalaska is oceanic with moderate and fairly uniform temperatures and heavy rainfall. Fogs are almost constant. Summer weather is much cooler than Southeast Alaska but the winter temperature is nearly the same.Dutch Harbor has also been the largest fisheries port in the United States, in terms of volume of seafood caught, for nearly every year since 1981.The state of Alaska owns a 3,900 feet long by 100 feet wide paved runway, where daily flights are scheduled. Because of the very harsh weather conditions around Unalaska Airport, about a fifth of those flights are cancelled. A seaplane base is also available.