Objectives <p>There is growing concern among researchers and practitioners that misunderstanding of the central acceptance-based foundations of mindfulness, and/or a lack of openness to mindfulness, may prevent recipients from fully benefiting from an intervention. The current study was the first to experimentally investigate the impact of mindfulness understanding and openness on the efficacy of brief mindfulness meditation. Specifically, it investigated how both variables influence state mindfulness change following meditation.</p> Method <p>Participants (<i>n</i> = 155) were randomly assigned to a sham or active mindfulness meditation condition. Pre-intervention measures included participants’ understanding of mindfulness (control vs. acceptance-based) and openness to mindfulness. State mindfulness levels were assessed before and after the intervention.</p> Results <p>Participants in the active mindfulness condition reported significantly larger increases in state mindfulness than the sham, allowing further exploration of the primary research question. Higher openness was found to significantly predict increases in state mindfulness, while understanding was not.</p> Conclusions <p>The current study provides preliminary evidence that higher openness to mindfulness practice leads to greater increases in state mindfulness following meditation. It also provides preliminary evidence that mindfulness understanding does not impact state mindfulness change following meditation. These findings emphasise the benefits of fostering open attitudes to mindfulness-based interventions (MBIs) to maximise treatment outcomes in clinical practice and suggest that the effectiveness of brief mindfulness meditation at eliciting mindful states is not compromised by misconceptions regarding its acceptance-based foundations. Major limitations discussed include placebo effects, suitability of the active and sham meditations, use of single item measures, and generalisability.</p> Preregistration <p>This study was not preregistered.</p>