Diblock copolymers (DBCs) of MOPEO-b-PCL containing biocompatible and biodegradable components: hydrophilic methoxypoly-(ethylene oxide) (Mn = 2.5 kDa = const) and hydrophobic poly(ε-caprolactone) of a variable chain length (Mn = 2.8 ÷ 24.3 kDa) were synthesized by an anionic ring-opening block copolymerization. Their chemical and microphase structure were characterized using FTIR, NMR, DSC and WAXS. Self-assembly of pure DBCs and those at the presence of a model drug prednisolon (PS) in dioxane/aqueous solutions was studied using visible spectroscopy and static light scattering. Increasing in the micellar stability at the PCL block lengthening and PS addition was revealed. The drug binding by DBC micelles due to hydrogen bonds and hydrophobic interactions was confirmed by FTIR.