The accompanying diagram shows a ‘family tree’ of Salishan languages. Each of the languages and dialects has its own native name; the names of the languages and dialects shown here are the those that traditionally appear in the linguistic and anthropological literature. This tree is based on the organization proposed by Thompson (1979). Another proposal (Kuipers 2002) places Bella Coola with the Coast branch.

Although Klallam is a separate language, it is very closely related to the dialects called Northern Straits:  Saanich, Samish, Lummi, Songish, and Sooke. Saanich, Songish, and Sooke have been spoken on southern Vancouver Island and neighboring smaller islands. Lummi and Samish have been spoken near Bellingham on the US side of the border. Most of the words in Klallam are the same or very similar to words in the Northern Straits dialects. A speaker of Lummi, for example, could learn to understand Klallam very easily, and vice versa.

The Klallam language itself has several dialects. Elwha Klallam, Becher Bay Klallam, Jamestown Klallam, and Little Boston Klallam are all slightly different from one another in the pronunciation and usage of some words.