This study evaluates an innovative tertiary stress management intervention that combines 0.1 Hz coherent breathing with blue light exposure using the ÉOS device. Conducted through a randomized-controlled crossover double-blind design in a workplace-based laboratory setting, the intervention’s effects on subjective stress, sleepiness, positive and negative affect along with heart rate variability (HRV) and EEG metrics were assessed using linear mixed-effect models. The intervention significantly reduced subjective stress by 31.23% (CI 21.41 % and 41.83 %), decreased sleepiness by 0.84 points (SE 0.17), and increased positive affect by 1.85 points (SE 0.54). No significant effect was found on negative affect. The findings suggest that integrating coherent breathing with blue light exposure can effectively mitigate acute stress and enhance mood without inducing sleepiness, potentially benefiting workplace performance. This study contributes to the understanding of stress management by demonstrating the potential of combined coherent breathing and blue light to improve well-being and performance in occupational environments. Future research should also compare interventions individually, explore long-term effects, and utilize diverse populations to further validate these findings.