The trimethylsilylation of polygalacturonic acid is investigated in formamide as reaction medium at elevated temperature employing 1,1,1,3,3,3‐hexamethyldisilazan (HMDS) or trimethylsilyl chloride (TMSCl) in combination with imidazole. The products obtained are characterized by size exclusion chromatography, NMR‐, and IR spectroscopy. Regarding the degree of substitution (DS), HMDS is a more reactive silylation reagent compared to TMSCl/imidazole. Products with DS values of 0.6 are obtained with TMSCl while HMDS yields products with DS of up to 1.8. Nevertheless, both reagents lead to the formation of side products. In the case of HMDS, formation of amid moiety occurs, which renders the carboxylic acid at the polymer backbone inaccessible for further transformations. Cross‐linking of polymer chains occurs applying TMSCl, which influences the molecular masses of the products obtained.