In today's world, increasing attention is being directed towards environmental preservation and biodegradability of materials. As a result, biodegradable polymers such as starch are being increasingly applied. Starch is a powder that needs to be plasticized to fully utilize its properties: softness, low cost, and high biodegradability. It transforms into thermoplastic starch (TPS) under the influence of mechanical and thermal energy in the presence of a plasticizer. The preparation of TPS completely disrupts the crystalline structure, resulting in a fully amorphous polymer. By blending TPS with other polymers, efforts are being made to create more environmentally friendly polymers due to their biodegradability. Mixing TPS with polycaprolactone (PCL) produces a TPS/PCL system with improved properties and potentially broader applications. An example of the use of the TPS/PCL system is in the production of food packaging bags, whose application is growing thanks to the rise in environmental awareness, all aimed at increasing the use of biodegradable polymers. Additionally, it is increasingly used for medical purposes. The rheological behavior of prepared TPS/PCL mixtures was examined, and mechanical properties were investigated using dynamic mechanical (thermal) analysis (DMTA). Measurements on an oscillatory rheometer were conducted by testing in a frequency range from 0.1 to 100 rad/s at a deformation amplitude of 0.5% and a constant temperature of 120 °C. The linear viscoelastic region was determined based on the dependence of the storage modulus on the deformation amplitude measured at 120 °C at a frequency of 1 Hz. In the DMTA method, the samples were subjected to torsion in the temperature range from -80 °C to 160 °C. The torsional action caused deformation or fracture of the sample depending on the ratio of TPS to PCL in the mixture. Analysis of the samples showed that increasing the PCL content decreases the viscosity of the system. The highest viscosity was recorded in the TPS/PCL (80/20) system. Therefore, systems with a TPS content greater than 30 wt.% behave like gels and have greater resistance to deformation, while systems with lower content behave like liquids. The addition of titanium dioxide (TiO2) filler alters the morphological properties and crystallinity of the mixtures, offering an additional possibility to control and influence their properties.