Prader-Willi syndrome (PWS) is the predominant genetic cause of obesity in humans. Recent clinical reports have suggested that micro-deletion of the Snord116 gene can lead to PWS, however, the extent of the contributions of the encoded snoRNAs is unknown. Here we show that mice lacking Snord116 have low birth weight, increased body weight gain, energy expenditure and hyperphagia. Consistent with this, microarray analysis of hypothalamic gene expression revealed a significant alteration in feeding related pathways that was also confirmed by in situ hybridisation. Interestingly, Snord116-/- mice kept at thermo-neutral conditions showed a further increase in body weight gain. Importantly, re-introducing Snord116 expression into the hypothalamus of otherwise Snord116 deficient mice imposes a lean phenotype confirming the critical role of Snord116 in controlling feeding and energy homeostasis as well as opens up the possibility for gene therapy approaches at least in a subset of PWS subjects in the future.