Drug delivery system (DDS) is a formulation or a device that enables the introduction of a therapeutic substance into the body and improves its efficacy by controlling the rate, time, and place of release. Requirements for a suitable DDS include: (i) high stability of the encapsulated drug; (ii) optimal drug loading; (iii) high encapsulation efficiency and yield; (iv) controlled drug release profiles; and (v) a simple, reproducible, and scalable preparation process. Drug-loaded nanoparticles (NPs), prepared by emulsion/dispersion polymerization or directly from preformed polymers, are generally based on biocompatible and biodegradable polymers. Moreover, NPs are characterized by: high drug encapsulation efficiency; improved drug bioavailability; solubility and retention time; enhanced chemical and biological stability; controlled drug release rate; wide variety of administration routes. Electrospinning is a versatile and economic technique that allows the incorporation of different drugs into a wide variety of polymers and blends. The electrospun fibers (ESFs) are much thinner in diameter and, thus, higher in surface-to-volume ratio than those obtained by conventional mechanical extrusion or spinning processes. The main objective of the present project is based on the preparation of two novel drug delivery systems, namely NPs and ESFs, starting from original polyester-based block copolymers. Polymers suitable for the preparation of these two DDS must meet several requirements, such as: biodegradability, biocompatibility, suitable mechanical properties, and ease of handling and processing. Recently, aliphatic polyesters, such as: poly(ε-caprolactone) (PCL) and polyadipates, have drawn attention in the preparation of DDS because they are considered to be preferable for ecological and economic reasons. However, there is no study regarding neither the synthesis of block copolymers based on PCL and poly(ethylene adipate) nor their processing as drug-loaded NPs or ESFs.