In a natural cavity, building cavity or nest box. Nest is made with grasses and forb stalks. Inner cup lined with finer grasses. Female builds the nest while male accompanies her. Commonly 4-6 which average 20.8 x 16.2 mm.
Eggs are oval with a smooth glossy shell.
Pale blue to bluish white and sometimes white in color. Female incubates for 2 weeks. From the time they hatch to the time they fledge is approximately 21 days. Often, they are less than one year old. Most Western Bluebirds mate for life.