We investigated school psychologists’ experiences of ethical strain (the frequency of ethical dilemmas at work and the stress caused by these dilemmas) and dilemma-related rumination outside working hours. Individual latent profiles were estimated at the study baseline based on these three dimensions. The psychologists’ weekly well-being (vigor, exhaustion, and sleep quality) was compared against their profile during the following three working weeks. The sample included 133 school psychologists, among whom four groups were identified: Low ruminators (39%), an Intermediate group (39%), High ruminators (20%), and Atypical outliers (2%). High ruminators fared least well in terms of weekly well-being. Of all the groups, they reported the lowest levels of vigor, the highest levels of exhaustion, and the lowest sleep quality. The study contributes to understanding how psychologists differ in their experiences of ethical strain, and highlights the role of ruminating: mental detachment from ethical demands is especially important for school psychologists’ well-being.