The development of new polymeric bionanocomposites with incorporation of cellulose nanocrystals (CNCs) has been attracting researchers and market attention. Some examples of biodegradable polymers being studied are thermoplastic waxy starch (TPS) and poly(ε-caprolactone) (PCL). Addition of TPS in polymers such as PCL has been used to make the final product cheaper and increase of biodegradability, but the addition of TPS causes a reduction in the properties of TPS blend. The incorporation of cellulose nanocrystals (CNCs) in the TPS provides the improvement of the final properties of the TPS, thus being able to make it more feasible to mix with the PCL. Macaúba, a native species of the Brazilian Pantanal, has a great potential for extraction CNCs from residues generated from their exploitation. This work aims to evaluate the thermal degradation temperature of biodegradable nanocomposites using cellulose nanocrystals from macaúba rachis fibers incorporated in a polymer matrix of PCL and TPS obtained from the waxy maize starch for agricultural applications of biodegradable materials, which are possible by extrusion and injection processing. Nanocomposites were obtained with 3.25; 6.5 and 13% by mass of CNCs in relation to the starch mass incorporated in the TPS phase in the blends of TPS/PCL 70/30. TPS/PCL 70/30 blend used as a matrix of the nanocomposites showed degradation onset at 268 ºC and the nanocomposites containing 3.25, 6.5 and 13% of CNCs in the TPS phase presented degradation start temperatures at 288, 274 and 245 ºC respectively. The nanocomposite containing 3.25% of CNCs showed an increase in thermal stability around 20 ºC. Therefore, the CNCs obtained from the macauba rachis improved the thermal properties of the TPS/PCL 70/30 blend, making it possible to add 70% by mass of TPS for the cheaper PCL compositions.