Background: The purpose of this study was to elucidate the cardioprotective effects and safety of seapolynol (polyphenol purified from Ecklonia cava) against adriamycin-induced cardiomyopathy in an animal rat model.Methods: Of total thirty rats, we divided 21 rats into Group 1 (low-dose seapolynol plus adriamycin,n=7), Group 2 (high-dose seapolynol plus adriamycin, n=7), and Group 3 (adriamycin,no seapolynol,n=7) for efficacy of seapolynol. We administrated seapolynol (32/64 mg/kg,daily,oral) one week before adriamycin(2.5mg/kg,weekly,intraperitoneal) was injected for 6 weeks. For safety of seapolynol, the other nine rats were divided into Group 4 (low-dose seapolynol only,n=3), Group 5 (high-dose seapolynol only,n=3), and Group 6 (control,n=3). We performed transthoracic echocardiography (15MHz linear array) was before (baseline) and after (4-,6-week) injection of adriamycin and analyzed cardiac function.Results: Adriamycin-induced cardiomyopathy was identified by Group 3 and there was no adverse interaction in Group 4, 5 and 6. Between Group 2 and 3 for 6 weeks, there were significant differences on left ventricular end diastolic/systolic dimension (LVEDD: 6.3짹0.4mm vs. 6.8짹0.3mm, p=0.012/ LVESD: 2.8짹0.5mm vs. 3.8짹0.3mm, p=0.001, respectively), fractional shortening (FS: 56.44짹6.26% vs. 44.16짹3.24%, p=0.001), left ventricular ejection fraction (LVEF: 82.65짹5.22% vs. 70.29짹3.42%, p<0.001), and the change of FS/LVEF (��FS: -2.08짹14.54% vs. -24.72짹7.89%, p=0.005/ ��LVEF: -2.01짹8.48% vs. -17.71짹4.95%, p=0.002),respectively. Between Group 1 and 3,there were significant differences on FS (52.91짹6.34% vs. 44.16짹3.24%, p=0.010), and LVEF (78.80짹5.81% vs. 70.29짹3.42%, p=0.008),respectively. Lastly,between Group 1 and 2, there were significant differences on LVEDD (7.2짹0.7mm vs. 6.3짹0.4mm,p=0.016), and LVEF (78.80짹5.81% vs. 70.29짹3.42%, p=0.008), respectively. Conclusion: Our Data showed that high-dose seapolynol was tolerable and more cardioprotective effects against adriamycin-induced cardiomyopathy in an animal rat model.