Deltamethrin (DMT), a toxic pyrethroid insecticide, contaminates soil and water, posing risks to humans and organisms. Phytoremediation using Plantago major was studied to remove DMT and its metabolites from polluted soil, enhanced by liquid silicon dioxide (SiO2, 750 mg L−1) and Bacillus subtilis AZFS3 (B. subtilis),107 CFU/mL) under greenhouse conditions. Our study assessed biochemical responses, including superoxide dismutase (SOD), catalase (CAT), hydrogen peroxide (H2O2), malondialdehyde (MDA), and detoxification gene expression in P. major roots and leaves subjected to DMT stress. SiO2 and B. subtilis desorbed DMT by 46.08 and 18.75 µg g−1, respectively. The longest half-life (t1/2) of DMT was 23.22 days in polluted soil alone, while the shortest (5.81 days) was observed in soil with P. major and B. subtilis. Soil with P. major plus SiO2 reduced DMT residues more effectively than B. subtilis and increased DMT accumulation in plant tissues. SOD and CAT activity peaked in roots and leaves treated with SiO2 and B. SUBTILIS, with lower H2O2 and MDA contents observed in SiO2 treatments. Additionally, DMT stress induced significant upregulation of cytochrome P450, glutathione S-transferases (GST), glycosyltransferases (GTs), and ABC transporter genes in P. major. SiO2 was more effective than B. subtilis in enhancing phytoremediation by promoting DMT degradation and metabolic detoxification pathways. This study highlights the potential of combining SiO2 and B. subtilis with phytoremediation to accelerate DMT removal and mitigate harmful pesticide residues in polluted soils and plants.