The theoretical contributions of Lazarus and Folkman have been foundational in the stress, appraisal, and coping scholarship for many decades. This entry provides a brief overview of their transactional theory which highlights the cognitive, emotional, and behavioral processes that individuals experience when faced with stimuli that are appraised as stressful and potentially harmful to one's well‐being. The theory brings to the forefront how this appraisal informs one's response to the stimuli. Gaps and critiques of the transactional theory are noted and a brief review of subsequent research addressing these theoretical constructs, including later work from Folkman and others advancing this theoretical foundation, is also offered. This includes highlighting current trends in the consideration of both positivity and negativity associated with stress and appraisals, future‐oriented proactive or health preventative behaviors, as well as relationally enacted coping processes. Relational and family scholars have emphasized the ways that stress, appraisal, and coping are enacted as joint ventures in collective and communal contexts and have further suggested that communal coping in and of itself is health promoting. Suggestions for future research are offered, including continued development and delineation among psychological, behavioral, and communicative conceptualizations and measurements of stress, appraisal, and coping.