Quality sleep is among the most important determinants of psychological and physical well-being. Insufficient sleep quality and quantity directly affect individuals; in turn, they indirectly affect the productivity, viability and safety of workplaces. Sleep issues also represent a global health concern for people and workplaces around the world. In addition to pharmaceutical aids, effective and accessible interventions need to address the underlying problems, as might be achieved by behavioural therapies or structured, cognitive interventions like mindfulness-based programs. The time intensity and relatively high costs of such tactics has limited their widespread adoption though. With a sample of 606 full-time working adults, the current study tests the potential effectiveness of a short, inexpensive, app-based, self-help mindfulness meditation programme for promoting sleep quality and quantity. Using a longitudinal randomised experimental design, the authors compared the utility of a 10-day mindfulness programme with a passive control group, as well as with an active control group that engaged in 10 days of mind-wandering exercises. Sleep benefits emerged immediately after the 10-day intervention but seemingly wore off about three months later. Acknowledging the interactions between sleep, depression and anxiety, we also measured the two latter variables. We also find that the intervention was effective on depression, but not on anxiety. These insights offer implications for both research and practice.