Methyl tert-butyl ether (MTBE) is a gasoline oxygenate additive used to enhance gasoline combustion by lowering carbon monoxide and hydrocarbon emissions, thus reducing air pollution. However, it has been identified as the second most common volatile organic contaminant of urban aquifers in the United States. Methyl tert-butyl ether has also been blended into two types of gasoline sold in Mexico by the state oil company (Petróleos Mexicanos) but is currently not monitored in groundwater. Early research on MTBE determined that it is unable to sorb to soils and sediments. The objective of this study is to determine if fine-grained materials with high organic matter (0.25–15.3%) have the potential for sorption of MTBE. The experiment consisted of sorption isotherms of loess from DeKalb, Illinois, and lacustrine sediments from Chalco, Mexico. Experiments were performed with various concentrations of MTBE and benzene (10, 50, 100, 500, and 1000 μg/L) at 25°C and 10°C. Methyl tert-butyl ether showed a retardation factor (R) as high as 1.856 ± 0.0130 for lacustrine sediments and 1.095 ± 0.0010 for loess at 25°C. Benzene showed retardation factors as high as 1.996 ± 0.0150 in lacustrine sediments and 1.775 ± 0.0050 in loess at 25°C. These results showed that sorption, and therefore, the retardation of MTBE in groundwater, is possible in fine-grained materials especially with high organic matter. This research increases the understanding of the fate and transport of MTBE and improves the knowledge to implement the optimal remediation method for sites contaminated by MTBE.