Novel thermosets were prepared by the base-catalysed reaction between a cycloaliphatic resin (ECC) and various thiol crosslinkers. 4-(N,N-Dimethylaminopyridine) (DMAP) was used as base catalyst for the thiol–epoxy reaction. A commercial tetrathiol (PETMP) and three different thiols synthesized by us, 6SH-SQ, 3SH-EU and 3SH-ISO, were tested. 6SH-SQ and 3SH-EU were prepared from vinyl or allyl compounds from renewable resources such as squalene and eugenol, respectively. Thiol 3SH-ISO was prepared starting from commercially available triallyl isocyanurate. A kinetic study of the mixtures was performed using differential scanning calorimetry. Stoichiometric ECC/thiol/DMAP formulations were cured at 120 °C for 1 h, at 150 °C for 1 h and post-cured for 30 min at 200 °C. The materials were characterized using Fourier transform infrared spectroscopy, thermogravimetric analysis and dynamic mechanical thermal analysis. The results revealed that the materials obtained from the synthesized thiols had higher thermal stability and glass transition temperatures than those obtained from the commercial PETMP. In addition, all the materials obtained exhibited very good transparency. This study proves the ability of multifunctional thiols to crosslink cycloaliphatic epoxy resins, leading to more flexible materials than those obtained by cationic homopolymerization of ECC or base-catalysed ECC–anhydride copolymerization.