This article is concerned with two aspects of how planning practitioners use survey-derived data; how planners integrate the limitations of survey questionnaires into practice, and the prevalence of such data within planning. Using a web survey ( n = 201) and interviews ( n = 18) of Canadian municipal planners, I find that survey data are heavily relied on, but many planners do not seem to be aware of cognitive biases when designing surveys, and those that are, have little knowledge of how they ought to mitigate them. To develop planners’ understanding of these biases and improve the survey data they collect, quantitative methods courses within planning curricula could respond by expanding beyond statistical analysis to incorporate survey design and “the total survey error approach” of survey methodology.