Weathered hydrocarbons in clay soils pose a persistent environmental hazard due to their low mobility and strong sorption to aged organic matter, resulting in limited bioavailability and complicating remediation efforts. Electrokinetic-driven bioremediation offers a promising solution, yet the optimal voltage for enhancing the bioavailability of weathered hydrocarbons, particularly under short duration, energy efficient operation and in the presence of synthetic surfactants such as Methyl Ester Sulfonate (MES) remains unclear. This study applied a two-stage treatment consisting of electrokinetic remediation (EKR) during 48 hours followed by 33 days of bioremediation. Three laboratory reactors were operated at different voltage gradients (17 V (1 V/cm), 34 V (2 V/cm), and 42.5 V (2.5 V/cm)). Total petroleum hydrocarbon (TPH) removal and changes in hydrocarbon degrading bacterial populations were evaluated. The 2 V/cm reactor treatments achieved the highest TPH removal efficiency (90.16%), outperforming the 1 V/cm (80.38%) and 2.5 V/cm (62.31%) treatments. Reduced performance at 2.5 V/cm was attributed to electrode polarization and microbial inhibition, highlighting a critical operational threshold. Statistical analysis showed that bioelectrokinetic remediation (BIO-EKR) had a significant effect on TPH removal, p < 0.001 and microbial population, p = 0.002. Voltage significantly affected TPH removal p = 0.042 but did not affect microbial population p = 0.520. No significant interaction was observed between voltage and remediation time. These findings demonstrate that moderate voltage, short duration electrokinetic pretreatment can substantially enhance bioremediation efficiency while reducing energy demand, providing an effective strategy for remediating weathered hydrocarbon contamination in low-permeability soils.