cAMP response element-binding protein (CREB) is one of the best known transcription factors in the development and function of the nervous system. In this report, we found that the regulator of calcineurin 1 (RCAN1), which is overexpressed in the brain of patients with Down syndrome, increased the phosphorylation of CREB and cAMP response element-mediated gene transcription in response to the activation of the intracellular cAMP pathway. Furthermore, we found that the increased activation of CREB signaling by RCAN1 depended on the ability of RCAN1 to inhibit calcineurin activity. Our data provide the first evidence that RCAN1 acts as an important regulatory component in the control of CREB signaling.