Adults weigh 66.8–108.5 g (2.36–3.83 oz), with females being larger than males on average as the species exhibits a dimorphism ration of 1.033.

[4][5] During the summer and winter, it displays a distinctive black median dorsal stripe along its back.

[5] The coastal subspecies is found solely in the redwood forest belt of California that extends from the Pacific coast to about 32 km (20 mi) inland, and ranges from the Eel River of Humboldt County in the south to the Klamath River of Del Norte County in the north.

[5] Allen's chipmunk is a primarily arboreal species, inhabiting coniferous forests and their dense shrubbery, as well as areas of adjacent chaparral.

[4] Allen's chipmunk is omnivorous, with its diet consisting of fungi, insects, seeds, flowers, and fruit.

Its diet is heavily dependent on geographical location and seasonality, mainly affecting the amount of fruit, flowers, and seeds consumed.

However, due to a lack of data on Allen's chipmunk, specifics on its life expectancy are unknown.

[11] Natural predators of Allen's chipmunk include hawks, owls, foxes, coyotes, snakes, badgers, and weasels.