The polymer blends are multiphase systems i.e. physical mixtures of two or more polymers. Properties of blends depend on the properties of their individual constituents, their morphology and interfacial adhesion between phases. The aim of this study was to investigate the impact of polyamide 12 (PA 12) and polylactide (PLA) on thermal and mechanical properties and PA12/PLA surface properties. Thermal, mechanical and surface properties were investigated for the starting polymers: PA12 and PLA and for the PA12/PLA blends of the different composition prepared in the Brabender kneader. Thermal properties were tested by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), while the mechanical properties were tested by a stretch test. The contact angle method was used to investigate surface properties. The obtained results indicate an increase in thermal stability of PLA by the addition of PA12 waste powder and a significant influence on the PLA crystallinity. The lowering tensile strength with the lowering elongation at break indicates poor adhesion between PA12 and PLA polymers. The obtained values of the adhesion parameters are consistent with the results of the mechanical properties.