Nurses use electronic medical record (EMR) systems to accomplish a variety of care-related tasks. Nurses, therefore, encounter a range of stressful situations and events related to using EMR systems, a phenomenon known as technostress. Previous research suggests that individuals appraise technostress differently. However, not much is known about the appraisal process of technostress. By integrating the literature on technostress, affordances, and appraisal theory, this paper introduces the appraisal theory of technostress, which is developed empirically through an interpretive case study involving interviews with hospital nurses. The appraisal theory of technostress explains how individuals process and appraise information about how to potentially act on technology-related stressful events through a system's features. Information about the event, and information about the action potential afforded by the system's features, is evaluated through an appraisal process that includes three appraisal checks: goal relevance, goal conduciveness, and value compatibility. The appraisal checks verify whether the action possibilities of the system's features align or misalign with an individual's goals and values related to action, and shape how the event and the system's features are appraised as challenge or hindrance techno-stressors. Overall, the study offers a novel theoretical perspective and methodological approach to conceptualizing and investigating technostress. More detailed contributions to research and practice are also discussed.