It covers the islands of Inchcailloch, Clairinsh, Torrinch, Creinch and Aber Isle, alongside areas of woodland and wetlands to either side of the mouth of the Endrick Water.

The reserve is managed by a partnership consisting of NatureScot, the RSPB Scotland and the Loch Lomond and The Trossachs National Park, along with the owners and tenants of the land under agreements.

[5] Within this framework NatureScot directly manage the islands of Clairinsh, Inchcailloch, Torrinch and Creinch, and land to the north of the Endrick Water.

Atlantic oakwoods are characterised by their lichens and mosses, which thrive in the damp conditions, and support many species of plants and birds.

[8] The makeup of woodland on each island, and on the mainland section, differs slightly, adding to the diversity of habitats at Loch Lomond NNR.

Unlike many other European rivers the Endrick has not undergone drainage or flood defence schemes: this considered to be a key factor underpinning the importance of the site from a nature conservation point of view.

A number of rare plants are found at the reserve, including elongated sedge, six-stamened waterwort, cowbane, summer snowflake and mudwort.

[14] Loch Lomond itself hosts populations of powan, whilst the Endrick Water supports brook lamprey and Atlantic salmon.

[20] Most of the mainland portion of the NNR also forms part of the Loch Lomond Special Protection Area (SPA).

[12] The woodland of Creinc is notable for its large coppiced wych elms and mature ash trees,[22] whilst its shoreline supports plants such as globeflower, columbine and goldilocks buttercup.