Research into both mindfulness and mind-wandering has grown rapidly, yet clarification of the relationship between these two seemingly opposing constructs is still absent. A first study addresses the relationship between a dispositional measure of mindfulness (Mindful Attention and Awareness Scale, MAAS) and converging measures of both self-reported and indirect markers of mind-wandering. Negative correlations between dispositional mindfulness and 4 measures of mind-wandering confirm the opposing relationship between the 2 constructs and further validate the use of the MAAS as a dispositional measure of mindfulness. A second study demonstrated that 8 minutes of mindful breathing reduces behavioral indicators of mind-wandering during a Sustained Attention to Response Task compared with both passive relaxation and reading. Together these studies clarify the opposition between the constructs of mindfulness and mind-wandering and so should lead to greater convergence between what have been predominately separate, yet mutually relevant, lines of research.