Objective: To explore the developmental toxicity and the potential toxicological mechanism of safflower (Carthamus tinctorius L.) on zebrafish embryos/larvae. Methods: Mortality, malformations and increased apoptosis induced by safflower were assessed in zebrafish embryos from 6 to 96 hours post-fertilization. Enzymes and genes in the anti-oxidative and apoptotic pathways were also assayed. Results: The lethal concentration 50 of safflower to zebrafish embryos was 345.6 mg/L. Hatching inhibition, abnormal spontaneous movement, depressed heart rate, pericardial edema, yolk sac edema, abnormal head-trunk angle, inhibition of melanin release, enlarged yolk, and short body length were observed in safflower-treated zebrafish. Additional apoptotic cells mainly appeared around the heart. Safflower exposure changed the activities of defense enzymes (SOD↑, CAT↑, MDA↑, GPX without trend), increased MDA content, decreased caspase-3 activity, and altered mRNA levels of related genes (ogg1↓, p53↓, Cu/Zn-sod↑, Mn-sod↓, cat↓, gpx↑). Conclusion: Safflower exhibits developmental toxicity for zebrafish embryos/larvae. The developing heart was speculated as the target organ of toxicity. Oxidative stress and increased apoptosis have roles in the developmental toxicity of safflower. This article provides a novel method to research the teratogenicity and possible mechanisms of toxicity of traditional Chinese medicines that are prohibited or contraindicated in pregnant women.