Nicasio (ni-kash'-oh, or ni-cah'-see-oh) is a census designated place in Marin County, California. It is located 8 miles (13 km) west-southwest of Novato, at an elevation of 194 feet (59 m).The Nicasio region is a hydrologic zone containing the four main drainages of Nicasio Creek up to the ridgelines defining their basin. This includes: the south fork of Nicasio Creek extending from Moon Hill, along the ridge separating Nicasio from San Geronimo and Samuel P.