Twenty-one species of mammals have been recorded in the national park, including koala, spotted-tail quoll and the little bent-wing bat.

[3] Sea Acres National Park contains one of the largest and most intact segments of coastal rainforest in New South Wales.

[4] The remnant rainforest area adjacent to Shelley Beach is noteworthy as much of this sea side type of forest has been cleared for agriculture, mining or housing.

The rare flat fork fern was recorded at Sea Acres, but its exact location is currently unknown.

[5][8] There are also non-rainforest areas which include grassland, banksia woodland and eucalyptus forest with tallowwood, blackbutt and Sydney blue gum.