Workaholism literature has been so far focused on individual differences in workaholic tendencies, considering the construct as a stable individual trait and highlighting its health and well-being consequences. Only recently, research has started inspecting the daily dynamics and potential consequences of state workaholism. In this preregistered study, we aimed at systematically investigating the within-individual fluctuations in workaholism levels and their potential short-term and delayed psychophysiological responses as captured by ambulatory assessment integrating subjective and objective data. Using an intensive longitudinal design over 10 workdays with 114 workers from various occupations (2,534 measurement occasions), we found higher systolic and diastolic blood pressure, emotional exhaustion, and sleep disturbances in workdays characterized by higher-than-usual workaholism symptoms. Moreover, the reactivity to state workaholism, as indexed by afternoon blood pressure, was found as a mediator of the subsequent prolonged activation indexed by bedtime blood pressure. Finally, we found evidence of a buffering effect of evening psychological detachment on the relationship between state workaholism and sleep disturbances. Overall, our results support the conceptualization of workaholism as a multilevel phenomenon that acts as an internal job-related demand by showing the typical strain reactions triggered by well-characterized external demands. This study contributes to the literature by highlighting that transient workaholism symptoms can result in significant short-term stress responses at different levels, providing new, robust, and multisource evidence that underlies the importance of effectively preventing and managing dysfunctional work investment since its early manifestation. (PsycInfo Database Record (c) 2024 APA, all rights reserved).