The best source of information on the population status of Western Wood-Pewee is the Breeding Bird Survey (BBS). Although the northern and mountainous portions of its range are poorly covered, overall reliability of the BBS is considered medium. BBS data indicate a large long-term decline, starting in the mid 1980s. The population is currently 53% lower than in the 1970s. Moderate to large declines have occurred in all Canadian Bird Conservation Regions where trend reliability is at least medium, except the Prairies and south-central British Columbia, which show little change.

The goal for Western Wood-Pewee is to increase the population to the level it was at in the early 1970s, based on the Breeding Bird Survey. Trend data show that Western Wood-Pewee is currently below its goal range and continuing to decline. Analysis considering the historical population loss and recent trend suggests that it is unlikely that the goal can be met by 2050, so the interim target is to reach 85% of the goal by 2050. Achieving this target, and ultimately reaching the national goal for this species, will require deliberate conservation action.