The UN Decade for Safe Water underscores the importance of evaluating the toxicities of industrial wastewater discharges to protect aquatic ecosystems. This study assessed the influent and effluent toxicities from a textile industrial establishment in Lagos State, Nigeria, using a 96-hour acute non-renewal bioassay system with juvenile Oreochromis niloticus. Various parameters, including pH, conductivity, color, total suspended solids (TSS), total dissolved solids (TDS), total alkalinity, total acidity, biological oxygen demand (BOD), chemical oxygen demand (COD), turbidity, and heavy metals, were analyzed in the textile industrial wastewater samples. The results indicated that most of the effluent parameters met the standards set by the Federal Environmental Protection Agency (FEPA) for industrial effluent discharge, including heavy metal concentrations. Mortality rates were recordedased on the wastewater concentrations (v/v), and the fish exhibited uptake of certain heavy metals from the wastewater. The derived toxicity indices revealed that the 96-hour LC50 values for the influent and effluent against O. niloticus were 49.46v/v and 325.43v/v, respectively, indicating that the influent was 6.58 times more toxic than the effluent. Test organisms displayed symptoms of toxicosis, including loss of equilibrium, erratic swimming, weakness, periods of quiescence, and death. This study emphasizes the importance of incorporating active biomonitoring of industrial effluent treatments at all stages to confirm treatment efficiency and ensure compliance with environmental safety limits in order to promote the UN Decade for Safe Water objectives.