Different calcined clays were found to have significant impact not only on the spread flow of cement paste, but also on characteristic rheological parameters due to their individual shear-dependent flow behavior. This study aims to establish a deeper understanding of the rheological behavior of calcined clay blended cements. At first, several polycarboxylate (PCE) comb polymers were selected to provide fluidity for the calcined clay (CC) suspensions which were prepared from pristine metakaolin, metamuscovite, metaillite and metamontmorillonite, respectively. By measuring zeta potential and sorption values, the dispersing effect of the PCEs was found to derive from PCE adsorption onto positively charged surfaces of the calcined clays, which was facilitated by the uptake of Ca2+ ions from the pore solution. The methallyl ether (HPEG) based PCE showed superior dispersing performance over methacrylate ester (MPEG) based PCE. Surprisingly, metaillite could not be dispersed satisfactorily, despite its high PCE adsorption. Moreover, the shear-dependent rheological behavior of the pure calcined clays (CCs) and of CC-OPC blends was studied to further investigate into the impact of calcined clays on the rheological characteristics of cement pastes. Shear-dependent rheology was measured at 0.1–600 rpm rotational speed using a Couette type viscometer. It was revealed that calcined muscovite, illite and OPC exhibit a shear-thinning (pseudoplastic) behavior whereas metakaolin showed slight shear-thickening (dilatant) and metamontmorillonite an almost ideal Newtonian (linear) relationship. Opposite to this, in blends with OPC, all calcined clays produced Bingham Plastic fluids. The Hershel-Bulkley model was applied for the fitting of the rheological curves.