A series of poly(butylene succinate) (PBS) nanocomposites were synthesized via in situ polymerization. These nanocomposites consisted of 0, 1, 3, and 5 wt.% of nano sepiolite. The effect of sepiolite addition on polycondensation progress was investigated by measuring the mixing torque. The results reveal a significant decrease in reaction time, indicating the catalytic capabilities of nano sepiolite. The existence of hydrogen bonding between nano sepiolite and PBS chains is revealed using FTIR spectroscopy. The presence of a growing secondary crystallization process, with the quantity of sepiolite, is observed based on the non-isothermal DSC curves. Non-isothermal crystallization kinetics from the melt state was studied using the Avrami, Tobin, and Hay models. Due to the secondary crystallization, only the Hay model gave a suitable fit. Deconvolution of melt crystallization shows that α and β forms of crystals are formed. The dispersion of nanoparticles was assessed using techniques such as XRD, SEM, and EDS. These methods revealed that the bundles of needle-like sepiolite were predominantly separated. Thermal stability of PBS was studied using TGA. A new thermal degradation kinetics model was proposed. The fit results of the suggested model were very good. Tensile stress, Young's modulus, elongation at break, and break energy were increased with the amount of nano sepiolite. The findings from the tensile test and Dynamic Mechanical Thermal Analysis (DMTA) provided evidence that the inclusion of nano sepiolite can enhance mechanical properties as a result of its elevated specific surface area. Subsequently, a hydrolytic degradation test was conducted in a basic solution, 0.5 N NaOH, and in phosphate buffer saline medium, at 37°C. it was observed that the addition of nano sepiolite to the PBS matrix, which contained 5 wt% of nano clay, significantly enhanced its biodegradability.