Contamination of the aquatic environment by plastic industrial products and their by-products is remarkable. Because of their physical, chemical, and biological degradation resistance, plasticizers can enter the food chain of living organisms, accumulate in the body and generate toxic effects. Here we determined the potential toxic effects of bis(2-ethylhexyl) phthalate (DEHP) plasticizer to larval (72 h post fertilization) zebrafish (Danio rerio) by analyzing changes in expression levels of stress-related genes (p53, rad51, and xrcc5) by the quantitative real-time polymerase chain reaction. Also, possible DNA damage by DEHP in larvae was determined. The concentration of DEHP (0-160 mg/l) that killed 50% of the larval zebrafish within 96 h was 54.02 mg/l. There was a concentration-related increase in DNA damage in cells from larvae exposed (96 h) to DEHP. DNA damage of 31.13% (mean +/- standard error of the mean) was observed in larvae at the highest sublethal DEHP concentration (10 mg/l). Some significant differences in the induction of stress-related genes were also observed in larvae exposed to DEHP relative to control (p < 0.05). The conclusion drawn from this ecotoxicological risk assessment is that, under present use and exposure patterns, DEHP presents a small hazard to zebrafish larvae.