In soft tissue engineering, there is a great emphasis on the production of scaffolds from biomaterials. They are often produced from decellularized extracellular matrix (dECM) hydrogels because during the decellularization process native cells are removed with the preservation of biological and chemical characteristics. Scaffolds must meet certain requirements such as mechanical stiffness and stability to support cell adhesion, growth, and development, in which dECM alone frequently does not suffice. Therefore, the physico-chemical and mechanical properties are modified with the addition of natural polysaccharides such as sodium alginate. In addition, the gelation of sodium alginate itself can be stimulated by the addition of calcium chloride, which directly affects its mechanical strength. Such preparation creates hybrid hydrogels of sodium alginate with calcium chloride and dECM. To characterize the hydrogels prepared from sodium alginate (3% and 5% wt%) and calcium chloride (1-5 and 8% wt%), their rheological behaviour was examined, determining the viscosity to investigate the influence of CaCl2 on the mechanical properties of gels. Hydrogels prepared by combining different concentrations of sodium alginate with dECM were characterized using differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR). In this way, the stability and potential newly formed bonds in the combined hydrogels were tested. The results of rheological testing showed that sodium alginate hydrogels with 5% calcium chloride were most applicable for further testing, The results of DSC tests showed that the 25 dECM/75 3% ALG sample is the most stable, and the FTIR analysis results indicate that the strongest bonds are in the 50 dECM/50 3% ALG sample. Thus, the results did not unequivocally point to the sample that can be considered the most suitable for future analysis, which commonly happens in testing the properties of hydrogels. Requirements for in vivo application and 3D printing are often contradictory and it’s necessary to carefully adjust parameters such as viscosity, degree of crosslinking and thermal properties for preparation of the appropriate hydrogel scaffold.