Metallodendrimers—dendrimers with included metals—are widely investigated as biocompatible equivalents to metal nanoparticles. Applications can be expected in the fields of catalysis, as chemical sensors in molecular recognition and as anticancer drugs. Metallodendrimers can also mimic certain biomolecules, for example, haemoprotein in the case of using a dendrimer with a porphyrin core. In previous papers, we showed the promising anticancer effects of carbosilane ruthenium dendrimers. The present paper is devoted to studying biocompatibility and the cytotoxic effect on normal and cancer cells of carbosilane ruthenium dendrimers labelled with fluorescent probe fluorescein isothiocyanate (FITC). The addition of fluorescent probe allowed tracking the metallodendrimer in both normal and cancer cells. It was found that carbosilane ruthenium dendrimer labelled with FITC in concentration up to 10 µmol/L was more cytotoxic for cancer cells than for normal cells. Thus, FITC labelled carbosilane ruthenium dendrimer is a good candidate for diagnostic imaging and studying anticancer effects of metallodendrimers in cancer therapy.