Notch proteins are the receptors for an evolutionarily highly conserved signalling pathway that regulates numerous cell fate decisions during development. Signal transduction involves the presenilin‐dependent intracellular processing of Notch and nuclear translocation of the intracellular domain of Notch, Notch‐IC. Notch‐IC associates with the DNA‐binding protein RBP‐Jκ/CBF‐1 to activate transcription of Notch target genes. In the absence of Notch signalling, RBP‐Jκ/CBF‐1 acts as a transcriptional repressor through the recruitment of histone deacetylase (HDAC) corepressor complexes. We identified SHARP as an RBP‐Jκ/CBF‐1‐interacting corepressor in a yeast two‐hybrid screen. In cotransfection experiments, SHARP‐mediated repression was sensitive to the HDAC inhibitor TSA and facilitated by SKIP, a highly conserved SMRT and RBP‐Jκ‐interacting protein. SHARP repressed Hairy/Enhancer of split (HES)‐1 promoter activity, inhibited Notch‐1‐mediated transactivation and rescued Notch‐1‐induced inhibition of primary neurogenesis in Xenopus laevis embryos. Based on our data, we propose a model in which SHARP is a novel component of the HDAC corepressor complex, recruited by RBP‐Jκ to repress transcription of target genes in the absence of activated Notch.