In this study, two novel chitosan-graft-poly(vinyl alcohol) copolymers are synthesized and used as water-soluble at physiological conditions polycations for preparation of smart microcapsules. The microcapsules provide growth and proliferation of eight mammalian cell lines, including hybridoma and tumor cells, at long-term cell cultivation in vitro. The microcapsules are stable in cell culture medium but can be dissolved by changing pH value of the medium (up to 8.0–8.2), thus making possible a simple release of the entrapped cells. Monoclonal antibody production by encapsulated hybridoma cells is demonstrated. Cultivation of tumor cells within the microcapsules allows the formation of 3D multicellular spheroids, which can be proposed as an in vitro model for anticancer drug screening.