This chapter aims to explicate a multilevel explanatory conceptualization of role of perfectionism in daily stress, coping, and adjustment process. It reviews studies of university students, community adults, and depressed patients which used daily diary method to examine stress and coping patterns that trigger and maintain daily negative and positive affect. The chapter discusses factor-analytic results identifying personal standards and self-critical higher-order dimensions of perfectionism and appraisal, coping, and affect constructs across both situational and dispositional levels. Daily engagement trigger patterns involve constructive social and self appraisals and engagement coping strategies that commonly facilitate one another to orient the individual's attention toward many daily stressors, and these patterns are linked to within-person increases in daily positive affect for the typical individual. Theory and research suggest that disengagement coping and engagement coping responses each have the ability to suppress or inhibit the other.