<p>Giant polyoxometalates (POMs) are of great interest across multiple research fields. In particular, they can serve as a structuring agents for the design of protein-based nanoparticles. Albumin is actively studied as a component of nanoformulation for drug delivery and “theranostics”. In the present study, we presumed the positively charged pockets on the albumin’s molecule surface as binding sites for {Mo₁₃₂} and {Mo₇₂Fe₃₀} POMs anions. The impact of the POM/albumin ratio in aqueous solutions on the particle size and zeta potential was investigated. Polyoxometalates demonstrated a more pronounced concentration-dependent variation in particle size with a narrower distribution compared to the decomposition products, which were employed as a reference to illustrate the significance of a nanosized structure. Albumin solutions containing {Mo₁₃₂} demonstrated enhanced colloidal stability and a higher proportion of small particles (less than 20 nm) in comparison to the {Mo₇₂Fe₃₀} containing solutions. The addition of {Mo₁₃₂} to the albumin solution enables the achievement of a negative zeta potential for particles as low as –21 mV. We demonstrated, that tumor cells are more susceptible to the influence of {Mo₇₂Fe₃₀}-albumin composition than normal cells.</p>