Additive manufacturing (AM) is presented as a great alternative to produce new metal alloys. Mg alloy WE43 is one of most relevant alloys for bioimplants due to its good mechanical properties and biocompatibility. However, its low corrosion resistance requires the use of coatings that can improve the corrosion behaviour of these alloys. Plasma electrolytic oxidation (PEO) is based on the growth of an oxide layer by means of high voltages (300V ‒ 600V) that incorporates various species from the electrolyte that can enhance corrosion resistance. Nevertheless, PEO coatings usually require an additional procedure post treatment in order to seal their external porous layer. Hydroxyapatite (HAp) is usually employed to promote bone growth and biocompatibility; additionally, its porous microstructure allows for the adhesion of other sealings that might improve the corrosion resistance. Polycaprolactone (PCL) is one of most used polymers for biomedical applications, mainly because of its biocompatibility and limited production of acid by-products. This study focuses on the development of a multilayer PEO/HAp/PCL system to investigate its effect on the corrosion behaviour of an AM WE43 Mg alloy after a heat treatment of 400ºC over 24h. The substrate before and after the heat treatment is characterized using several techniques such as: optical and scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The coatings were also characterized by SEM, EDS, and XRD, their roughness was measured with an optical profilometer, and water contact-angle measurements were performed. For the corrosion evaluation, electrical impedance spectroscopy (EIS) measurements were performed up to 3 days on Hank’s solution at 37ºC. The results reveal the influence of the multilayer coating on the corrosion behaviour, providing a comparative analysis with the substrate.