Azo dyes are used widely as color additives in food, drugs, and cosmetics; hence, there is an increasing concern about their safety and possible health hazards. In the present study, we chose 4 azo dyes tartrazine, Sunset Yellow, amaranth, and Allura red and evaluated their developmental toxicity on zebrafish embryos. At concentration levels of 5 to 50 mM, we found that azo dyes can induce hatching difficulty and developmental abnormalities such as cardiac edema, decreased heart rate, yolk sac edema, and spinal defects including spinal curvature and tail distortion. Exposure to 100 mM of each azo dye was completely embryolethal. The median lethal concentration (LC), median effective concentration (EC), and teratogenic index (TI) were calculated for each azo dye at 72 hours postfertilization. For tartrazine, the LC was 47.10 mM and EC value was at 42.66 mM with TI ratio of 1.10. For Sunset Yellow, the LC was 38.93 mM and EC value was at 29.81 mM with TI ratio of 1.31. For amaranth, the LC was 39.86 mM and EC value was at 31.94 mM with TI ratio of 1.25. For Allura red, the LC was 47.42 mM and EC value was 40.05 mM with TI ratio of 1.18. This study reports the developmental toxicity of azo dyes in zebrafish embryos at concentrations higher than the expected human exposures from consuming food and drugs containing azo dyes.