Cysteine string protein (CSPalpha, also called DnaJC5) is unique among J proteins. Similar to other J proteins, CSPalpha interacts with and activates the ATPase of Hsc70s (heat shock proteins of 70 kDa), thereby harnessing the ATPase activity for conformational work on client proteins. In contrast to other J proteins, CSPalpha is anchored to synaptic vesicles, as well as to exocrine, endocrine and neuroendocrine secretory granules, and has been shown to have an essential anti-neurodegenerative role. CSPalpha-null organisms exhibit progressive neurodegeneration, behavioural deficits, and premature death, most likely due to the progressive misfolding of one or more client proteins. Here we highlight recent advances in our understanding of the critical role that CSPalpha plays in governing exocytotic secretory functions.