Santa Barbara County occupies a roughly rectangular area at the southern end of California's Central Coast region. The county is bordered by the Pacific Ocean to its south and west, with the region's topography consisting primarily of coastal hills and river valleys. This gives rise to a broad spectrum of terroirs reflected in Santa Barbara County's diversity of grape varieties. In the cooler Santa Maria Valley, the leaning is clearly towards cooler-climate varieties – Pinot Noir and Chardonnay – while in the warmer Happy Canyon of Santa Barbara, just to the south, Cabernet Sauvignon, Syrah and Grenache thrive.

From the Santa Ynez Mountains in the south and west to the San Rafael mountain range in the east, the landscape is truly varied. The many rivers which flow down from the mountains towards the Pacific Ocean have carved out valleys and coastal plains over the millennia. The coastal valleys are oriented east-west, channelling cool ocean breezes and sea fog eastwards through the valleys. These climatic factors keep the vineyards in the county's western reaches cool with a moderate climate, while the vineyards to the east experience larger diurnal temperature variations as these cooling effects gradually dissipate.

Overall Santa Barbara County has a coastal climate with a long growing season, allowing the grapes extended hang time to develop mature flavours and a much-valued balance of sugars and acids. This is something of a luxury at such low latitudes (34.5 degrees north) and allows the county's winemakers to make relatively balanced wines, unaffected by the high alcohol content associated with warmer climates. The cool climate also results in higher acidity, balancing the mature flavours of the grapes and increasing their aging potential. Low rainfall, too, reduces the risk of the fruit spoiling, allowing it to ripen fully.

Santa Barbara County's soils are just as diverse as its climate – from sandy, silt and clay loams, to diatomaceous earth, to patches of limestone and chert. This unique blend of climate and soils creates ideal growing conditions for a range of grape varieties, with Santa Barbara County producing some of the most sought-after (and most expensive) wine grapes in California.

Six of the county's wine sub-regions currently hold official AVA status: Santa Maria Valley, Santa Ynez Valley, Sta. Rita Hills, Happy Canyon of Santa Barbara, Ballard Canyon and Los Olivos District.