Psychotherapy is used commonly to treat a variety of mental illnesses, yet surprisingly little is known about its biological mechanisms especially in comparison with pharmacotherapy. In this review we survey the current knowledge about changes in brain function following psychotherapeutic intervention that are detectable with current neuroimaging techniques. We also consider the possible role for neuroimaging in refining clinical diagnoses and predicting treatment outcome, which would benefit both clinical decision-making and the cognitive neuroscience of psychotherapy.