The present article interprets mindfulness from the point of view of the effects of language and cognition on human action. Relational Frame Theory is described to show how human suffering is created by entanglement with the cognitive networks made possible by language. Mindfulness can be understood as a collection of related processes that function to undermine the dominance of verbal networks, especially involving temporal and evaluative relations. These processes include acceptance, defusion, contact with the present moment, and the transcendent sense of self. Each of these components of mindfulness are targeted in Acceptance and Commitment Therapy, and there is some evidence that they underlie the therapeutic changes induced by this approach. The relation between the present approach to mindfulness and other approaches is discussed.