Although evidence has been mounting that supervisor support training interventions promote employee job,health, and well-being outcomes, there is little understanding of the mechanisms by which such interventionsoperate (e.g., Hammer et al., 2022; Inceoglu et al., 2018), nor about the integration of suchorganizational-level interventions with individual-level interventions (e.g., Lamontagne et al., 2007). Thus,the present study attempts to unpack the mechanisms through which supervisor support training interventionsoperate. In addition, the present study examines an integrated Total Worker Health® interventionthat combines health protection in the form of supervisor support training (i.e., family supportive supervisorbehaviors and supervisor support for sleep health) with a health promotion approach in the form of feedbackto improve sleep health behaviors. Using a cluster randomized controlled trial drawing on a sample of 704full-time employees, results demonstrate that the Total Worker Health intervention improves employee jobwell-being (i.e., increased job satisfaction and reduced turnover intentions), personal well-being (i.e.,reduced stress before bedtime), and reduces personal and social functional impairment at 9 monthspostbaseline through employee reports of supervisors’ support for sleep at 4 months postbaseline, butnot through family supportive supervisor behaviors. Effects were not found for general stress oroccupational functional impairment outcomes. Implications are discussed, including theoretical mechanismsby which leadership interventions affect employees, supervisor training, as well as the role ofintegrated organizational and individual-level interventions