The California red-legged frog is found in California and extreme northern Baja California, northwestern Mexico. This species now occurs most commonly along the northern and southern Coast Ranges, and in isolated areas in the foothills of the Sierra Nevada mountains. The current southernmost California populations are on the Santa Rosa Plateau in Riverside County, and within the Upper Las Virgenes Canyon Open Space Preserve in the Simi Hills in eastern Ventura County, near the community of West Hills. In 2015, egg masses from the nearby Simi Hills were introduced to two streams in the Santa Monica Mountains. Juvenile frogs were found living at the locations a year later.