Objectives <p>This research assessed the effects of the Mindfulness-Based Strategic Awareness Training (MBSAT). MBSAT follows the 8-session structure of established mindfulness courses such as Mindfulness-Based Stress Reduction (MBSR) and Mindfulness-Based Cognitive Therapy (MBCT). However, it is a personal and professional development training for non-clinical contexts geared toward healthy individuals with the aim of improving their broadly defined well-being.</p> Method <p>We conducted an experimental intervention study with a waitlist control group with working adults in Switzerland. Most of the 43 participants were randomly assigned to participate either in the MBSAT (<i>n</i> = 23) or a waitlist (<i>n</i> = 20) for subsequent participation in the MBSAT after completion of the data collection.</p> Results <p>Compared to the control condition, the MBSAT training group participants scored lower on measures of negative well-being, such as stress, alexithymia, and worry, and higher on measures of positive well-being, such as sleep quality, non-attachment, psychological need satisfaction, flourishing, and work engagement after the intervention. Mediation analyses found that greater interoception in the training condition mediated these various well-being outcomes.</p> Conclusions <p>The study provides quantitative evidence to validate MBSAT as an effective intervention for increasing well-being in a non-clinical setting with active working adult participants. The research highlights the role of interoception as a potential mediator of the benefits of mindfulness-based interventions.</p> Preregistration <p>This study was not preregistered.</p>