Buddhist and contemporary psychological theories propose that training attention and awareness in mindfulness meditation is a fundamental mechanism of mindfulness, essential for producing its salutary effects. Yet, the empirical foundation for this central idea in mindfulness science is surprisingly small due to a limited methodological capacity to measure attention and awareness during mindfulness meditation. Accordingly, we set out to study these processes (N = 143) via a novel behavioral paradigm measuring the objects and temporal dynamics of mindful awareness during meditation – the Mindful Awareness Task (MAT). Using this paradigm, we empirically characterized attention and awareness during mindfulness meditation. We provide novel behavioral evidence indicating that, as long-theorized, attention and awareness during mindfulness meditation are related to previous mindfulness meditation practice, attitudinal qualities of mindfulness, attention regulation, and mental health. We found that in contrast to widely held assumptions, sustained attention and executive functions, as measured via common cognitive-experimental tasks, may not be meaningfully related to the cognitive capacities trained and expressed in mindfulness meditation. Furthermore, we found that the accuracy of self-reported mindfulness is, paradoxically, dependent on behaviorally measured capacities for mindful awareness. Collectively, our behavioral findings reveal that, as long-theorized, attention and awareness during mindfulness meditation may indeed be fundamental to the practice, cultivation, and salutary functions of mindfulness. Findings indicate that the MAT paradigm may overcome significant limitations of extant measurement methods, and thereby enable future scientific insights into attention and awareness in mindfulness meditation and their salutary effects.