Petroleum pollution is an important environmental problem in countries with oil industry. In addition to the harmful effects on human health, petroleum pollution impacting soil and water resources and natural ecosystems, could adversely affect living organisms, especially plants. This study was done to investigate the effects of petroleum pollution on soil hydraulic properties and water repellency in Bakhtiardasht region, Isfahan. Polluted locations with various soil texture and oil concentration (total petroleum hydrocarbons, TPHs in the range of 2?10%) and adjacent non-polluted locations were selected to be representative in the green space around the Isfahan Oil Refinery. In the first part, the impact of soil petroleum pollution on in situ unsaturated infiltration and soil hydraulic properties was evaluated using tension infiltrometer at four consecutive matric suctions (15, 10, 5 and 2 cm). Soil hydraulic parameters were then predicted using Wooding's analytical and DISC numerical methods. Persistence of soil water repellency was assessed using water drop penetration time (WDPT) and soil structural stability was evaluated using the wet sieving method and mechanically dispersible clay (MDC). The data were analyzed using two-way ANOVA of 4 soil texture groups and 4 levels of petroleum contamination (none, TPHs of zero; low, TPHs of 1?3%; moderate, TPHs of 3?6%; high, TPHs 6%) with dissimilar replicates. In the second part which was done in the laboratory, petroleum pollution of water (well water in the region) was also considered in addition to the aged-petroleum pollution of the soils. Soil samples with specific degree of compactness (80% of the reference bulk density) were repacked. The soils were wetted and dried for 13 cycles using unpolluted and petroleum-polluted waters. Then, saturated hydraulic conductivity ( K s ) and water characteristic curve of the soil samples were measured using constant-head method and at 16 matric suctions, respectively. The soil water characteristic data were modeled using van Genuchten and Durner dual-porosity models and soil hydraulic parameters were predicted. Furthermore, pore size distribution, Dexter's physical quality index ( S Dexter ), and soil available water for plant (AW) were calculated. Several indices for soil water repellency were measured/calculated using molarity of ethanol droplet (MED), capillary rise method (CRM) and intrinsic sorptivity of water-ethanol. Results of the first part showed that cumulative infiltration into the soil was significantly decreased due to petroleum pollution. Likewise, petroleum pollution significantly reduced K s and near-saturated hydraulic conductivity, soil sorptivity ( S ) and steady-state flow rate ( q ) at all matric suctions. Results of numerical analysis also indicated that petroleum pollution significantly decreased K s and saturated ( ? s ) and near-saturated water contents. Overall, petroleum pollution up to TPHs of 6% did not considerably affect water infiltration and soil hydraulic properties, but high pollution (TPHs 6%) could significantly alter these properties. A positive and significant relation was found between log WDPT and TPHs independent of soil texture (i.e. TPHs/clay). Presence of petroleum hydrocarbons in soil significantly increased the water-stable aggregates and decreased MDC. Results of the second part showed that petroleum pollution of soil and water intensified soil hydrophobicity (i.e. significant increase in soil-water contact angle and water repellency indices). Through increased stability of pores and macroporosity, petroleum pollution resulted in significant and non-significant increase of ? s and K s , respectively. Besides the S Dexter was significantly increased as a result of petroleum pollution. Despite greater ? s and S Dexter in polluted treatments, soil was rapidly dewatered with matric suction increment and consequently AW severely decreased due to lower water retention in capillary pores. Results of fitting Durner model indicated that petroleum pollution in soil significantly affected parameters of structural pores, such as higher slope at the first inflection point, greater contribution of structural pores to water retention and lower matric suction at the first inflection point. However, water pollution did not significantly influence soil water retention properties and parameters. Overall, it might be concluded that one of the reasons for plant cover degradation in Bakhtiardasht region is petroleum wastes (especially for the locations having TPHs 6%) which intensifies soil water repellency, decreases water infiltration, alters soil hydraulic properties and consequently decrease soil water retention and available water for plant.