Previous studies have demonstrated a relation between dispositional optimism and lower pain sensitivity, but the causal status of this link remains unclear. This study sought to test the causal status by experimentally inducing a temporary optimistic state by means of writing about and visualizing a future best possible self. In addition, we explored pain expectations and (situational) pain catastrophizing as possible underlying mechanisms of the link between optimism and pain. Seventy-nine university students participated in a cold pressor task (CPT). Before the CPT, half of them received the optimism manipulation and the other half a control manipulation. Induced optimism was related to lower pain intensity ratings during the CPT compared to the control group, thereby experimentally confirming causality. This effect was not explained by pain-related expectations about the task. Situational pain catastrophizing, however, did seem to mediate the relation between optimism and pain. This study is novel in that it confirms the causal status of optimism towards pain. Additionally, the results reveal that positive interventions might provide a useful alternative in reducing pain catastrophizing as an extremely relevant target in pain treatment. (C) 2012 International Association for the Study of Pain. Published by Elsevier B. V. All rights reserved.