There is growing research interest regarding the significance of mindfulness in the workplace. Within this body of knowledge, research investigating the effects of mindfulness interventions on employee health and well-being has strong practical implications for organizations. A sound understanding of the current state of the workplace mindfulness intervention literature will help inform the suitability of these interventions within the workplace domain, and how to improve the conduct and communication of intervention-oriented research. Accordingly, in this article, we systematically review 40 published articles of mindfulness interventions in the workplace to identify ways in which these interventions could be improved, and how to overcome methodological concerns that threaten study validity. Studies selected for review were published peer-reviewed, primary empirical research studies written in English, with a focus on a workplace mindfulness intervention. We discuss a range of issues evident within this body of literature, including conceptualizations of mindfulness; the adaptation of protocols to work settings; internal validity in relation to random allocation and control conditions; the use of manipulation checks; attrition, adherence, acceptability, and maintenance of interventions; utilizing objective cognitive measures; examining organizational and well-being outcomes; and establishing boundary conditions. Overall, this review provides a resource to inform scholars to advance this line of inquiry and practitioners who are considering implementing a mindfulness intervention for employees.