Oligo(epsilon-caprolactone)-modified polycyanurate networks were synthesized by thermal polycyclotrimerization of dicyanate ester of bisphenol E in the presence of a dihydroxy-telechelic poly(c-caprolactone) (PCL) oligomer with varying compositions. Using FTIR, gel fraction content and density measurements, it has been proved that the main part of the reactive modifier was chemically incorporated into the PCN network structure. According to the thermal behavior of the polymer networks as investigated by TGA, they can be divided into two groups. The first group of systems with low modifier content (i.e., up to 20 wt %) is characterized by one stage of decomposition under nitrogen, and two stages under oxygen. A second group of systems with higher modifier content is generally characterized by two stages of decomposition in nitrogen and three stages in oxygen. DSC and DMTA investigations have shown the occurrence of at least a two-phase structure in all the samples. The PCN/PCL-based hybrid networks can be effectively used as precursors for the generation of porous PCN thermosets, as evidenced by FTIR and SEM.