Flexibly using different emotion-regulation (ER) strategies in different situational contexts, such as domains, has been argued to promote effective emotion regulation. Additionally, emotion regulation processes may change with age as narrowing time horizons shift emotion-regulation preferences. The purpose of the present study was to examine the occurrence and effectiveness of flexible emotion regulation in response to daily hassles from different domains within the age range from adolescence to old age. Participants, ranging from 14 to 88 years old (N = 325), completed an experience-sampling study of approximately 9 days over a 3-week period. At each momentary assessment, participants reported on their hassles, emotion-regulation strategies, and affect. As expected, strategy use varied across individuals and domains. For example, emotion expression and suppression were typical responses to interpersonal hassles, whereas social sharing was often used in response to work/school hassles. In situations wherein hassles included multiple life domains, participants reported the use of more emotion-regulation strategies than for single-domain hassles. Although flexible emotion regulation was evident in participants’ responses to hassles, the expectation that it would be associated with lower hassle reactivity was not confirmed. These patterns were, for the most part, consistent across ages. This study contributes new insights into situational characteristics that are associated with emotion-regulation flexibility, showing that hassles domains are important for strategy selection, and that this holds from adolescence to old age. It also suggests that such defined emotion-regulation flexibility is not as strongly linked to emotion-regulation effectiveness as has been previously suggested.