This study investigated the potential of Brassica napus L. to remediate heavy metals from surgical industry wastewater through the application of neem (Azadirachta indica L.) leaf extract and nZVI. Plants exposed to untreated wastewater exhibited significant reductions in growth and photosynthetic pigments. However, the combined application of neem extract and nZVI improved plant height by 318%, number of leaves by 300%, leaf area by 329%, and root length by 63% at 100% wastewater concentration. The treatment also decreased oxidative stress indicators, including hydrogen peroxide (H2O2) by 16% in leaves and 8% in roots, malondialdehyde (MDA) by 21% and 39%, and electrolyte leakage (EL) by 27% and 50%, respectively. In contrast, antioxidant enzyme activities increased, with peroxidase (POD) enhanced by 47% in leaves and 81% in roots, superoxide dismutase (SOD) by 97% and 59%, ascorbate peroxidase (APX) by 55% and 29%, and catalase (CAT) by 38% and 52%. The accumulation of heavy metals also rose substantially under the combined treatment, with Ni, Cd, and Pb increasing by 33–126%, 23–106%, and 52–74% in roots; 29–87%, 36–140%, and 50–155% in stems; and 46–73%, 36–74%, and 71–186% in leaves, respectively, compared with control plants.