Objective To investigate the effects of tetrandrine on early development in zebrafish embryos and the expression of multidrug resistance gene abcb4 and its mechanisms. Methods We used a drug toxicity test to analyze the mortality, hatching rate, heart rate, and deformity rate of zebrafish embryos treated with tetrandrine. Wild-type zebrafish embryos were divided into a blank control group, doxorubicin treatment group, vinblastine treatment group, tetrandrine treatment group, tetrandrine combined with doxorubicin treatment group, and tetrandrine combined with vinblastine treatment group. Drugs were administered to each group of embryos until the fifth day, and the embryos were then used for the experiment. Expression of the abcb4 gene was detected using real-time fluorescent quantitative PCR, and drug resistance was detected using the Rhodamine 123 test. Results Compared with the control group, low-dose tetrandrine had no teratogenic lethal effects on zebrafish embryos. High-dose tetrandrine significantly inhibited embryonic hatching rate and had clear lethal and teratogenic effects. Compared with the control group, the mRNA of the abcb4 gene increased when treated with doxorubicin and vinblastine alone, but decreased when exposed to tetrandrine combined with doxorubicin and vinblastine. The Rhodamine 123 experimental result showed evidence of drug resistance in zebrafish treated with doxorubicin and vinblastine alone, and indicated that tetrandrine combined with doxorubicin and vinblastine could reverse drug resistance. Conclusions Tetrandrine has low toxicity for zebrafish embryos early in development, and can reverse drug resistance to doxorubicin and vinblastine. These data suggest that tetrandrine may improve sensitivity to chemotherapy drugs and thus may enhance the therapeutic effect.