The aim of this work was the synthesis of high-entropy oxide with the chemical formula (TiZrHfNbTa)O11. Four synthesis methods were used: citric, coprecipitation, sol-gel, and hydrothermal. Chlorides of niobium (NbCl5), tantalum (TaCl5), hafnium (HfCl4), and zirconium (ZrCl4), as well as titanium butoxide (Ti(C4H9O)), were used as starting reactants for all four syntheses. All synthesized samples were characterized using Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM/EDXS). Based on SEM/EDXS results, it was concluded that the contents of niobium, tantalum, hafnium, and zirconium in all synthesized samples are approximately equal, while the content of titanium is almost twice as high, likely due to its higher reactivity since it is introduced into the reaction mixture in the form of an alkoxide. High-entropy oxide samples that showed the highest degree of homogeneity in SEM/EDXS analyses and good matching of elemental molar ratios with theoretical values were further analyzed using X-ray diffraction analysis (XRD). Based on XRD analysis, it was concluded that the diffractograms of annealed high-entropy oxides match the literature data, confirming that all applied methods are suitable for the synthesis of HEO with the targeted composition. From the diffractogram of the precursor obtained by the hydrothermal method, it was concluded that this synthesis method does not directly yield an oxide without an additional annealing step.