The object of this study was to evaluate the single oral dose toxicity of Low Molecular Weight Fucoidan (LMF) in male and female rats. LMF was administered to female and male SD rats as an oral dose of 2,000, 1,000 and 500 mg/kg (body wt.). Animals were monitored for the mortality and changes in body weight, clinical signs and gross observation organ weight and histopathology of 14 principle organs were examined upon necropsy. As the results, no LMF treatment related mortalities, clinical signs, changes on the body and organ weights, gross and histopathological observations against 14 principle organs were detected up to 2,000 mg/kg in both female and male rats except for some sporadic findings not LMF treatment related toxicological signs. Therefore, $LD_{50}$ (50% lethal dose) and approximate LD of LMF after single oral treatment in female and male rats were considered over 2,000 mg/kg - the limited dosages recommended by KFDA Guidelines [2005-60, 2005], respectively.