Existing structural analyses of emotion-regulation (ER) strategies have relied on retrospective, dispositional assessments, ignoring the within-person structure (i.e., intraindividual strategy groupings based on momentary covariances) and variability in strategy use across time and contexts. We conducted multilevel exploratory factor analyses on self-reported daily use of 11 strategies (i.e., acceptance, behavioral avoidance, distraction, experiential avoidance, expressive suppression, procrastination, reappraisal, reflection, rumination, savoring, social support) in clinical (N = 129) and student (N = 109) samples with intensive longitudinal designs. At the between-person level, two factors—Engagement and Avoidance—emerged in both samples. A different structure was found at the within-person level, with four factors in the student sample (i.e., Attentional Shift, Acceptance, Avoidance, Emotional Expression) and three in the clinical sample (i.e., Attentional Shift, Avoidance, Emotional Expression). The validity of these factors was examined via their associations with daily internalizing symptoms and affect. Implications for naturalistic ER strategy use and clinical assessment/intervention are discussed.