The purpose of the study was to determine the cytotoxicity of commercial silver, gold, and copper nanocolloids towards two established cell lines (NIH/3T3 and GMK) and primary chick embryo cell culture (CECC), using routine colorimetric assays: MTT, NRU, and LDH, which enable a preliminary evaluation of the mechanism of cytotoxic effect of the tested substances. The MTT assay evaluates the activity of mitochondria, NRU assay reveals the damage to lysosomes, while LDH assay shows injuries to the cytoplasmic membrane. The NRU assay proved to be non-applicable to the tested nanocolloids, most probably due to the interaction of nanoparticles with neutral red dye, which affected the colorimetric reaction. The MTT assay was more sensitive than LDH because the intercellular effect of a substance occurs before permanent damage to the cytoplasmic membrane. Silver nanocolloid was distinguished by the highest cytotoxicity, irrespective of the applied cell model, although the other two metals showed some cytotoxic effects as well, with gold nanocolloid being more toxic than copper one. Although the primary chick embryo cell culture, as a model reflecting more faithfully the conditions in a living organism than continuous cell lines, was undistinguished by elevated tolerance to the most toxic silver nanocolloid, it showed the tendency to recovery from the growth suppression with longer exposure after the application of less toxic gold and copper nanocolloids.