Objective Experience sampling studies on Big Five–related behavior show that people display the whole spectrum of each trait in their daily behavior, and that desirable Big Five states—especially state Extraversion—are related to positive mood. However, other research lines suggest that extraverted and conscientious behavior may be mentally depleting. The present research examined this possibility by extending the time frame of the measured personality processes. Method A 12‐day experience sampling study (N = 48; observations = 2,328) measured Big Five states, mood, stress, and fatigue five times a day. Results Extraverted and conscientious behavior were concurrently related to positive mood and lower fatigue, but to higher fatigue after a 3‐hour delay. These relations were not moderated by personality traits. The relation between extraverted behavior and delayed fatigue was mediated by the number of people the person had encountered. Whether the person had a goal mediated the relation between conscientious behavior and delayed fatigue. Conclusion Extraverted and conscientious behavior predict mental depletion after a 3‐hour delay. The results help reconcile previous findings regarding the consequences of state Extraversion and provide novel information about the consequences of state Conscientiousness.