This study investigated if trait mindfulness and its components, mindful attention, acceptance, and non-judging correlate negatively with self-reported and indirect markers of mind-wandering. The 552 participants of the study completed an anonymous online questionnaire consisting of trait mindfulness and mind-wandering scales. They also completed the computer-based Sustained Attention to Response Task (SART), an objective measure of mind-wandering. The total mindfulness score and acceptance and non-judging subscale scores were strongly negatively correlated with both self-reported trait mind-wandering (TMW) and SART indices of mind-wandering. In contrast, attention was significantly positively correlated with both. These findings suggest that trait mindfulness conceptualised as a multi-component construct, but not a uni-component one, is probably an opposing construct to trait mind-wandering. Furthermore, mindfulness and its components, acceptance and non-judging, are associated with a reduction in the more common form of SART errors. However, only the acceptance component made a unique contribution to the variance in TMW and SART performance. Therefore, it is advisable for researchers to specify whether they investigated mindfulness as a uni-component or multi-component construct. Furthermore, it would be beneficial if future research investigates the relationship of mindfulness and its components with mind-wandering further by also incorporating a measure of state mindfulness.