Introduction ER plays an important role in our everyday life. Different ER strategies can be distinguished and differ in their ability to alter emotional responding. All strategies have in common that cognitive control has to be exerted to implement these strategies. However, only little is known about cognitive costs of ER strategies. In general, it is assumed that “expressive suppression” should require more cognitive control, because one has to constantly change emotional responding. Supportive evidence showed that memory was impaired after use of “expressive suppression”, but not after “reappraisal”. Aims The aim of the present study was to investigate whether two ER strategies “expressive suppression” and “detachment” require different amounts of effort. Therefore, we first wanted to replicate findings that associated the early pupillary response with effort during ER. Second, we wanted to extend these findings by comparing two different ER strategies. Furthermore, associations with broad and narrow personality traits were explored. Methods In two experiments, N = 110 and N = 52 participants conducted an emotion regulation paradigm. Participants had to use “expressive suppression” and “detachment” during inspection of positive and negative pictures. They also had to decide, which strategy they wanted to reuse at the end of the paradigm. Effort was assessed subjectively via ratings and objectively via pupillometry. Broad and narrow personality traits included Big Five and the Emotion Regulation Questionnaire. Results Although “detachment” was more effective in downregulation of subjective arousal (Study 1: F(1.85,202.15) = 26.9, p < .001, ηp² = .20; Study 2: F(1.93,98.57) = 13.33, p < .001, ηp² = .21), about two thirds of the participants did reuse expressive suppression, because it was perceived as less effortful. Subjective effort ratings show significantly lower effort ratings for “expressive suppression” compared to “detachment” (Study1: F(1,109) = 4.25, p = .042, ηp² = .04; Study 2: F(1.88,92.14) = 7.03, p = .002, ηp² = .13). However, differences in effort were not reflected in pupillary data. Broad and narrow personality traits were neither associated with the preferred strategy, nor with subjective and objective effort measures. Conclusions The present research adds evidence to the topic of differential costs of ER strategies. Our findings suggest that people tend to use the strategy that is perceived as less effortful, even though it might not be the most effective strategy.