In a non-minimal Higgs framework, we present a novel mechanism in which the CP violating dark particles only interact with the SM through the gauge bosons, primarily the $Z$ boson. Such $Z$-portal dark CP violation is realised in the regions of the parameter space where Higgs-mediated (co)annihilation processes are sub-dominant and have negligible contributions to the DM relic density. We show that in these regions of the parameter space, the $Z$-portal CP violating DM can still thermalise and satisfy all experimental and observational data. We discuss the implications of such phenomena for electroweak baryogenesis.