A number of prior studies have found evidence for the expectancy-disconfirmation theory of citizen satisfaction with public services, which holds that citizens judge public services not only on experienced service quality but also on an implicit comparison of service quality with prior expectations. But the evidence to date has been based on surveys (observational studies) and on subjective measures of expectations and performance, which are likely endogenous. Thus, the present study aimed to test the expectancy-disconfirmation theory of citizen satisfaction with public services using an experimental method. Participants in an Internet panel (N = 964) were randomly assigned to receive either low- or high-expectations statements from a hypothetical government official and to view either low- or high-performance street cleanliness photographs, in an online survey experiment. The findings are in line with previous research and generally confirm the core relationships in the theory, although the effect of expectations varied by age and political ideology. Because this study is a true randomized experiment, it provides better evidence than previous studies regarding the true causal nature of these relationships.