Abstract <p>In this research, two fine and coarse filter sands (S1 and S4) and two combinations (S2 and S3) of these sands were used to discover the effects of soil textural heterogeneity on the soil water retention curve (SWRC). SWRCs were estimated using HYPROP. The soil graduation results revealed that the soil S1 and S4 were the most uniform, whereas the soil S2 and S3 showed a relatively significant degree of heterogeneity. Simulation results revealed that the van Genuchten hydraulic parameter α increased linearly with increasing the grain size and was found to be more sensitive to <i>D</i>50. Results further indicate that for soils with similar sorting and uniformity coefficients, the soil containing a higher proportion of coarse particles exhibited a larger van Genuchten parameter α. While an increase in grain sizes caused a nonlinear reduction in the parameters of <i>m</i> and <i>n</i>. Hence, an increase in fine grains in heterogeneous soils significantly increased the parameters <i>m</i> and <i>n</i>. Furthermore, as soil porosity increased, the value of parameter α increased in the coarse and heterogeneous sands with a high proportion of coarse grains. However, this trend differed for fine-grained soils, despite their relatively high porosity, the value of parameter α remained lower than in the other soils. Overall, the results suggest that soil particle size and consequently pore size distribution exerts a stronger influence on the van Genuchten parameters than soil sorting and uniformity coefficients.</p>