The aim of this study was to demonstrate blocked sites for imazethapyr sorption in Oxisols surface under brazilian tropical and subtropical conditions.  It was used six subtropical and five tropical soil samples and their size fractions (2000-250, 250-53, 53-20, 20-2 e <2 µm) obtained by physical fractionation. The pseudo-total iron and aluminum (Fe_t and Al_t) and low crystallinity forms of Fe and Al (Fe_o and Al_o) was extracted using sulfuric acid  and ammonium oxalate, respectively and experimental soil sorption coefficients (K_d-exp) were determined by Batch experiments using ¹⁴C labeled imazethapyr. The sorption on the percentage by weight of each fraction was used to calculate the relative contribution (%RC) of each fraction in the whole soil sorption and its sum allowed for the calculation of the theoretical soil sorption coefficient (K_d-teo). The means of %RC, K_d-exp and K_d-teo was compared by Tukey Test (ρ < 0.01). The K_d-exp ranged 0.72 to 2.83 L kg^-1 (2.03 ± 1.19 L kg^-1) in subtropical and 0.27 to 1.64 L kg^-1 (0.98 ± 0.56 L kg-1) in tropical soils. The greater %RC was observed in silt fractions (53 to 2 µm) and in tropical soils were reported the greater values (53 to 87%) compared to subtropical (39 to 53%). The difference between K_d-teo e o K_d-exp was more pronounced in tropical (1.07 to 2.51 L kg^-1) against subtropical soils (0.33 to 1.15 L kg^-1) and it means there are more blocked sites for imazethapyr sorption in tropical soils. Moreover, this difference was positively correlated with Fe_t, Fe_o, Al_t and Al_o levels in silt fraction (0.75; 0.70; 0.63; 0.59; < 0.01; respectively) which shows that presence of cementing agents like Fe and Al oxides in this fraction favors the blocking of sites in the tropical condition and explains their smaller K_d-exp compared to subtropical soils.