Online reviews are effective information-sharing tools due to their word-of-mouth characteristics. The extant literature has considered reviews as independent variables that influence business performance, while the environmental factors shaping these reviews remain under-explored. We examine the impact of COVID-19-related environmental uncertainties on changes in review prosumption (production and consumption) behavior. Based on the stimulus-response theory, with COVID-19 as the stimulus and prosumption as the response, we examined the changes in the characteristics of online reviews. Using the difference-in-differences methodology, we analyze online reviews of restaurants in two US cities that experienced different levels of COVID-19 impact. On the production side, we find an increased use of contextual terms and negative sentiments. On the consumption side, we find an increase in review usefulness and a decline in funniness. The results are robust, supported by coarsened exact matching and falsification tests. We conclude with a discussion of the study’s implications and contributions.