<p>The objective of this work was the thermal and spectroscopic characterization of arbidol hydrochloride and its compatibility study in mixtures with starch derivatives (sodium starch glycolate, pregelatinized starch and β-cyclodextrin) using thermal analysis methods, i.e., differential scanning calorimetry (DSC), thermogravimetry (TGA), hot-stage microscopy (HSM) and spectroscopic methods such as Fourier transform infrared spectrometry (FTIR), X-ray powder diffraction (PXRD) and also thermogravimetry coupled with Fourier transform infrared spectrometry (TGA-FTIR). A comparison of thermoanalytical and spectroscopic data of mixtures against data of ingredients in isolation demonstrates the occurrence of changes, especially in the case of arbidol hydrochloride mixture with sodium starch glycolate, indicating incompatibility between these ingredients. In turn, FTIR spectra of mixture with pregelatinized starch and PXRD pattern of mixture with β-cyclodextrin subtle changes in bands or diffraction lines were found. Mixing arbidol hydrochloride with β-cyclodextrin probably also leads to the formation of an inclusion complex that contributes to increased solubility of active substance. However, the highest changes in the structure of arbidol hydrochloride were revealed after mixing it with sodium starch glycolate, which, as a superdisintegrant, may contribute to increasing solubility of active substance.</p>