The islands feature outstanding rock formations and diverse landforms including shallow reefs, sand spits, beaches and dense rainforest-clad slopes. They also host important seabird rookeries.

Known as high continental islands, the forested slopes of the Barnard islands rise steeply from the sea. Heights of the islands vary from 19–95 m. The Barnard islands have a fascinating geological history dating back 420 million years. The older North Barnard islands are metamorphic rock outcrops while the younger South Barnard islands are layers of well-preserved volcanic tuff with steeply dipping basalt dykes cut through these layers.

The rocky slopes of the Barnard islands are densely cloaked in rainforest, with diversity increasing with the size of the island. Mangroves fringe parts of the islands and coastal plants border the shores. The South Barnard islands (Sister and Stephens islands) are an important breeding site for seabirds. Six species of terns have been recorded nesting there, mainly in the dense vegetation next to the shore. Twenty-three species of woodland birds have also been recorded on and around the Barnard islands.

The Barnard Island Group National Park is part of the 'sea country' of the Mandubarra Traditional Owners.

In the late 1800s, a bech-de-mer fishing settlement was built on Sisters Island. Six boats and a large Aboriginal workforce occupied the island until the settlement was lost in a cyclone in 1890. A small lighthouse was built on Kent Island in 1897. It was staffed until a cyclone in 1918 forced the evacuation of the lighthouse keeper and his family, after which the lighthouse was automated. Jessie, Bresnahan, Hutchinson, Sisters and Stephens islands have been protected as national park since 1936. Kent and Lindquist islands are Commonwealth islands.