Ecological momentary assessment (EMA) allows researchers to explore how experiential, physiological, and behavioral processes unfold over time in natural settings. Although increasingly used in mindfulness research, EMA remains a neglected methodology with untapped potential. In this chapter, we discuss some of the benefits and applications of this naturalistic data capture methodology. We argue that EMA could lead to a deeper understanding of the role of mindfulness in daily life if (a) passive sensors are used in conjunction with self-report queries; (b) momentary assessments are gathered to tailor interventions based on participants’ changing internal and external context; (c) within-person analytical approaches are favored, be it in terms of trajectories, variability patterns, or mechanisms of action; and (d) EMA is integrated within dyadic studies. In addition, we discuss the challenges associated with EMA and offer guidelines regarding the reporting of EMA studies to enable their replication and comparison.