The use of polluted urban lake water for vegetable irrigation presents a critical trade-off between agronomic benefits and food safety risks. This study evaluated the effects of irrigation with heavy metal-contaminated water from Ramgarh Lake, Gorakhpur, on the growth, yield, and heavy metal accumulation in radish (Raphanus sativus L. cv. NRD 45). A two-year pot experiment (2024–2025) compared tap water irrigation (control) with raw wastewater from the lake's outflow channel. Polluted water significantly enhanced seed germination (94.2% vs 81.9% in control), vegetative growth (33.7% increase in plant height), and fresh root yield (36.6% increase). However, substantial heavy metal accumulation occurred in both soil and edible tissues. Lead concentrations in radish roots (1.58 mg/kg) exceeded the FAO/WHO permissible limit of 0.30 mg/kg by over fivefold, while cadmium, arsenic, copper, chromium, and zinc remained within safety thresholds. Bioaccumulation factors ranged from 0.313 (As) to 0.628 (Pb), indicating efficient metal uptake. These findings demonstrate that while Ramgarh Lake water offers agronomic value through nutrient supplementation, its use for radish irrigation poses significant food safety concerns due to lead contamination, necessitating careful management and continuous monitoring.