Activating AMPK or inactivating calcineurin slows ageing in Caenorhabditis elegans(1,2) and both have been implicated as therapeutic targets for age-related pathology in mammals(3-5). However, the direct targets that mediate their effects on longevity remain unclear. In mammals, CREB-regulated transcriptional coactivators (CRTCs)(6) are a family of cofactors involved in diverse physiological processes including energy homeostasis(7-9), cancer(10) and endoplasmic reticulum stress(11). Here we show that both AMPK and calcineurin modulate longevity exclusively through post-translational modification of CRTC-1, the sole C. elegans CRTC. We demonstrate that CRTC-1 is a direct AMPK target, and interacts with the CREB homologue-1 (CRH-1) transcription factor in vivo. The pro-longevity effects of activating AMPK or deactivating calcineurin decrease CRTC-1 and CRH-1 activity and induce transcriptional responses similar to those of CRH-1 null worms. Downregulation of crtc-1 increases lifespan in a crh-1-dependent manner and directly reducing crh-1 expression increases longevity, substantiating a role for CRTCs and CREB in ageing. Together, these findings indicate a novel role for CRTCs and CREB in determining lifespan downstream of AMPK and calcineurin, and illustrate the molecular mechanisms by which an evolutionarily conserved pathway responds to low energy to increase longevity.