The article presents the results of studies of the influence of multicomponent modifier on the properties of cement pastes and self-compacting concretes. To reduce the cost of self-compacting concretes as well as to enhance their properties in fresh and hardened state the multicomponent modifier has been developed. It consists of ground granulated blast furnace slag, superplasticizer on the base of sulphonated naphthalene formaldehyde condensate, shrinkage-reducing admixture based on the polypropylene glycol derivative, and sodium sulphate set accelerator. The workability of SCC mixtures is considered from the rheological properties of cement pastes formulated from self-compacting concrete. The properties of fresh SCC have been tested according to EFNARC Committee’s suggestions. A partial replacement of Portland cement with granulated blast-furnace slag decreases hydration activity of the cementitious material resulting in contributing to higher flowability of cement paste. Shrinkage-reducing admixture in a combination with superplasticizer provide the effect of decreasing apparent viscosity of Portland cement-slag pastes. Sodium sulphate set accelerator coupled with superplasticizer and shrinkage-reducing admixture increase both the apparent viscosity of cement-slag paste and slump retention of SCC mixture. The multicomponent modifier provides an improvement of the properties of fresh (increased slump flow and slump retention) and hardened (28-day compressive strength comparable to control sample and decreased drying shrinkage) SCCs.