The smallest of the California Channel Islands, Santa Barbara Island, lies 38 miles of the coast of San Pedro, and is made up of 639 acres. Thought to be formed by volcanic activity, the island is diverse in it's many habitats, including canyons, steep cliffs, beaches. Having never had a land bridge to the mainland, there are many marine terraces that can be seen as a result of the islands uplifting process. These terraces slope away from the two main hills on the island: North Peak and Signal Peak. Two rocks also lie off the island; Shag Rock near the north shore, and Sutil Island off the southwest coast. Santa Barbara Island's isolation from the mainland is even more evident by the fact of their being no good sandy beaches, only rocky ones that are mostly submerged at high tide, leaving steep cliffs around most all of the island. There are also six named caves on the eastern side of the island. The island of Santa Barbara supports no trees, few shrubs, and in total about 120 different species of plants, with most of the vegetation lush in the spring and dry in the summer. Of the 120 different species of plant life on the island, 55 of those belong in the sunflower and grass family.

Santa Barbara Island supports only one terrestrial mammal; an endemic subspecies of deer mouse, and only one lizard, the endangered island night lizard, which is also found on the islands of San Clemente and San Nicolas. A haven for bird life due to it's isolation from predators, at least seventy types of birds live on Santa Barbara Island, including peregrine falcons, both Costa's and Allen's hummingbirds, horned larks, and California brown pelicans. The endemic Santa Barbara Island song sparrow is thought to have been extinct since the late 1960's. Marine mammals such as the northern elephant seal, harbor seal, and the California sea lion can also be seen on the island. Otters flourished on the island in the early 19th century, but have since been exterminated there due to over hunting.