Abstract Ground hydrocarbon contamination is a grave consequence of fossil fuel consumption, making it increasingly unsustainable. Consequently, researchers worldwide have been compelled to conduct a large number of studies on the geotechnical aspects of hydrocarbon-contaminated soils. Still, the complications arising from the integration of geotechnical complexities with diverse hydrocarbon properties present a substantial research need. The assessment of the foundation bearing capacity in hydrocarbon-contaminated soils is of paramount importance, especially given that numerous contaminated sites either house significant industrial facilities or are earmarked for critical infrastructure projects. This study investigates the shear strength and bearing capacity of gas oil-contaminated coastal sands using laboratory testing and physical modeling, with a special focus on the combined influence of the degree of saturation and relative density. Footing’s shear failure mechanisms were analyzed based on predicted and measured bearing capacity values. Findings show a decrease in the friction angle with a contamination increase, while the apparent cohesion initially rises before declining. Furthermore, the study revealed that the foundation’s bearing capacity exhibited an increase up to a specific contamination level, followed by a subsequent decrease. This increase is circa 90 and 100 percent at a 5 percent contamination content for loose and dense sand, respectively. Comparing the predicted and measured bearing capacity results shows that the general shear failure mechanism has occurred in the dense subgrade, while the loose subgrade’s failure mechanism is more inclined towards local shear failure. Keywords: contaminated soils; sand; sustainability; environmental geotechnics; bearing capacity