The frogs breed in small temporary ponds, lakes, in potholes, in overflows from rivers and lakes, or in slow moving rivers. Males arrive at the breeding sites first, calling the females to them. Breeding is temperature-dependant, only when the air temperature reaches a certain temperature does breeding begin. The food that the California red-legged frog preys upon differs with the age and size of the frog. Adult frogs eat insects, arachnids, and molluscs.
Juvenile frogs prey largely on invertebrates, such as insects and molluscs.
Tadpoles or larvae probably feed on algae. Adult frogs are mostly nocturnal while juvenile frogs are active diurnally, and nocturnally. Feeding occurs along shoreline and surface of water. During the day the red-legged frog inhabits the land. When a predator approaches the red-legged frog uses it's powerful legs to escape to the safety of the water.