- A paired male and female search for nest sites together, inspecting cavities to see if they are suitable.
- The females do almost all of the nest construction, gathering grasses, straw, pine needles, moss, other plant fibers, and fur from the ground and carrying it to the nest. She lines the nest cup with grasses, rootlets, feathers, horsehair, and sometimes bits of plastic.
- Western Bluebirds exhibit cooperative breeding; 2–14% of pairs have helpers at the nest. Helpers are typically juveniles from a previous brood, although adults may also help nesting pairs if they do not have their own territory or if their own nest has failed.
- Western Bluebirds can nest up to three times per season.