Recent research has shown that mindfulness moderates the negative emotional reactivity associated with neuroticism. In two studies, we investigated how neuroticism and mindfulness are associated with subjective well-being (SWB), assuming a moderated mediation. In Study 1, 147 participants (74.2% female, M = 34.3 years, SD = 11.9) completed an online survey. Mindfulness partially mediated but did not moderate the relationship between neuroticism and SWB, indicating that low levels of mindfulness were partially accountable for lower SWB in individuals high in neuroticism. In Study 2, 108 participants (80.6% female, M = 25.2 years, SD = 6.6) completed daily diaries for 6 days. We found evidence for a moderated mediation in trait as well as daily measures of mindfulness and SWB, in that the lack of mindfulness could explain around one quarter of the negative association between neuroticism and SWB. This mediation was moderated by neuroticism itself in Study 2, in that mindfulness was only a significant mediator for high levels of neuroticism. Our findings demonstrate that negative emotional reactivity associated with neuroticism is partially due to low levels of mindfulness, which offers a promising future research avenue for the role of mindfulness.