The aim of this research is to develop a new methodology to obtain bioactive coatings on bioinert and biodegradable polymers that are not intrinsically bioactive. In this study three types of materials were used as substrates: (i) high molecular weight polyethylene (HMWPE) and two different types of starch based blends (ii) starch/ethylene vinyl alcohol blends, SEVA-C and (iii) starch/cellulose acetate blends, SCA. Two types of baths were originally proposed and studied to produce novel auto-catalytic calcium–phosphate (Ca–P) coatings. Then, the coated surfaces were analyzed by scanning electron microscopy and energy dispersive spectroscopy (SEM/EDS), as produced, and after different immersion periods in SBF. The evolution of Ca and P concentrations was determined by induced-coupled plasma emission (ICP) spectroscopy. The crystalline phases present on the films formed on the different material surfaces, after a certain soaking time, were identified by thin-film X-ray diffraction (TF-XRD). The obtained results indicated that it was possible to coat the materials surfaces with a Ca–P layer with only 60 min of immersion in both types of auto-catalytic solutions. Furthermore, it was possible to observe the clear bioactive nature of the Ca–P coatings after different immersion periods in a simulated body fluid (SBF). The results from TF-XRD confirmed the presence of partially amorphous Ca–P films with clearly noticeable hydroxylapatite peaks. These new methodologies allow for the production of an adherent bioactive film on the polymeric surfaces prior to implantation, which may allow for the development of bone-bonding, bioabsorbable implants and fixation devices.