Gum-based food thickeners are widely used for diet modification for patients with dysphagia in Korea. In this study, the rheological properties of two commercially available gum-based food thickeners (xanthan gum and xanthan–guar gum mixture) marketed in Korea were determined as a function of concentration. The steady and dynamic shear rheological properties of the food thickeners in water were investigated at five different concentrations (1.0 %, 1.5 %, 2.0 %, 2.5 %, and 3.0 % w/w). Both food thickeners showed high shear-thinning fluid characteristics (n = 0.14–0.19) at all concentrations (1.0–3.0 %). In general, the thickener with the xanthan–guar gum mixture showed higher values for steady shear viscosity compared to that with xanthan alone, whereas it showed lower dynamic rheological parameter values. Steady and dynamic rheological parameters demonstrated differences in rheological behaviors between the gum-based food thickeners, indicating that their rheological properties are related to the type of gum and gum concentration. In particular, the type of gum played a role in the time-dependent flow properties of the gum-based food thickeners. Appropriately selecting a commercial food thickener appears to be of great importance for dysphagia therapists and patients.