Berry Island was part of the Cammeraygal clan’s land and contains aboriginal carvings, middens, a smoke stained cave and a stone tool grinding site. The Gadyan Walk - a 20-minute (750 metre) loop - was developed with the assistance of the Metropolitan Aboriginal Local Land Council and North Sydney Council -  with interpretive signage describing the aboriginal significance of points around the island.

Berry Island was known to be a fishing, hunting and camping site for Aboriginal communities with evidence of the Aboriginal way of life including shell middens and axe grindings still visible today.

In the early 19th century, Edward Wollstonecraft attached the small island to the mainland by constructing a stone causeway over the mud flats. After he died the property passed to his sister and her husband Alexander Berry. Public protests saw that the island was dedicated as a nature reserve for public recreation in 1926, along with Balls Head Reserve.

In the 1960s the mudflats were filled in to create the grassed area that exists today.

Berry Island consists of relatively untouched remnant Hawkesbury Sandstone vegetation, one of the most pristine bushland areas in North Sydney with Sydney Red Gums and Red Bloodwoods with a stunning understorey of flowering shrubs of White Spider Flower, pink flowering Crowea, Wattles, Banksias and the green and red bells of Correa. Shallow soils throughout the interior of the island supports a lower shrubland of Tick Bush, which makes important habitat for Ringtail Possums. Some locally rare plant species can also be found on the island, including Acacia longissima, Banksia oblongifolia and Grey Ironbark.

Berry Island is home to a few bird species, lizards and Ringtail Possums. Masked Plovers can be seen regularly on the lawn verge and Welcome Swallows are often seen gliding above the mown grassed area feeding on insects. A wildlife corridor was first planted along the grass verge in 1998.