Protein Serine Kinase H1 (PSKH1) was recently identified as a crucial factor in kidney development and is overexpressed in prostate, lung and kidney cancers. However, little is known about PSKH1’s regulation, leading to its classification as a “dark” kinase. Here, we used biochemistry and mass spectrometry to define PSKH1’s consensus substrate motif, protein interactors, and how interactors, including Ca2+ sensor proteins, promote or suppress activity.