Objectives : Paranoia is common in the general population and can impact on health, emotional well-being and social functioning; therefore effective interventions are needed. Brief online mindfulness-based interventions (MBIs) have the potential to be an easily accessible, low cost treatment for non-clinical populations. There is promising evidence for brief online MBIs for anxiety and depression however at present there is no research investigating whether they can benefit people with paranoia in the general population. Therefore the current study explored whether a brief online MBI increased levels of mindfulness and reduced levels of paranoia in a non-clinical population. The mediating effect of mindfulness on any changes in paranoia was also investigated. Method: 110 participants were randomly allocated to either a two week online MBI involving 10 minutes of daily guided mindfulness practice or to a waitlist control condition. Measures of mindfulness and paranoia were administered at baseline, post-intervention and one-week follow-up. Results: Analysis of the data indicated that there were significant group by time interactions for levels of paranoia and mindfulness skills. Participants in the MBI group displayed significantly greater reductions in paranoia and increases in mindfulness when compared to the waitlist control group. Mediation analysis demonstrated that change in mindfulness skills mediated the relationship between intervention type and change in levels of paranoia. Conclusions: This study provides evidence that a brief online MBI can increase mindfulness skills and significantly reduce levels of paranoia in a non-clinical population. Furthermore, increases in mindfulness skills from this brief online MBI can mediate reductions in non-clinical paranoia. The limitations and clinical implications of this study are discussed.