Recent evidence indicates that mindfulness is associated with adult attachment, such that individuals with a secure attachment style also tend to be more mindful. In the present experiment, we extend prior cross-sectional research by examining whether priming attachment insecurity (anxiety and avoidance) leads to a decrease in state mindfulness and whether this is mediated by decreased state emotion regulation. Priming attachment anxiety led to a decrease in state emotion regulation which, in turn, was associated with decreased state mindfulness. That is, when individuals experience heightened anxiety about relationships and abandonment, they experience difficulties in the regulation of emotion, which reduces capacity for mindfulness. No such effects were found for priming attachment avoidance. Results of the present research provide experimental evidence that attachment anxiety may be related to low mindfulness via difficulties in emotion regulation and provides some preliminary evidence of the social foundations of mindfulness.