A surface-tailored organoclay (palmitic acid-tailored Arquad^®-modified bentonite, ABP) was prepared for the selective adsorption of cadmium in the presence of polycyclic aromatic hydrocarbon (PAH) contaminants in a long-term contaminated soil. The efficiency of the organoclay (ABP) and the effect of its parent clays were assessed concerning the microbial viability, metal immobilization and PAHs bioavailability and biodegradation in a long-term (70 days) soil incubation study. The surface-tailored organoclay (ABP) increased the bacterial growth by 5–7 fold than the control and parent clay-amended soil. With an increased effect of aging, the ABP immobilized more Cd from the soil solution (2-folds higher than the control soil), and simultaneously increased the bioavailability (1.6–1.8 fold) of low molecular weight PAHs related to the control soil and the parent clay-amended soils. The surface-tailored organoclay (ABP) could also increase the mineralization of ¹⁴C-labeled phenanthrene by ca. 1.3-fold relative to the control experiment under a 25-days of incubation.