The Ukiah Daily Journal reports that the county's Board of Supervisors on Tuesday voted unanimously to make the declaration, citing an "imminent threat of disaster" from drought conditions.
The state Department of Water Resources said Mendocino is the first to request state drought assistance.
Officials hope the declaration will result in state funds and assistance in developing a drought plan.
Gov. Jerry Brown has convened a task force to help decide if a statewide drought emergency is warranted.
State water managers say they will be able to deliver just 5 percent of the water sought by municipal agencies and nearly a million acres of farmland.
Overall water use decreased again in September compared to last year in the Sacramento region. Water providers are also pumping less groundwater, despite a heavier reliance on it in the drought.
If a flood were to hit Twitchell Island in the Sacramento-San Joaquin Delta it would threaten much of California’s water supply. It’s why emergency management agencies are holding flood-fighting exercises during a drought.
UC Davis researchers have identified 'high priority' dams in California where releasing water may be a key for the survival of native fish species.
California Governor Jerry Brown says the state can lead the way with its water policies just as California is leading the way with initiatives for renewable energy and climate change.
A winter forecast from NOAA's Climate Prediction Center Thursday shows the California drought may persist or intensify in parts of the state.