This study investigates the effects of single and combined seaweeds diets on growth performance and ammonia-nitrogen production of the sea cucumber Holothuria impatiens under controlled laboratory conditions. Three naturally available seaweeds Caulerpa racemosa, Cystoseira indica and Jania rubens were used to feed sea cucumber juveniles, which averaged 6.09 g in weight at the beginning of the experiments. Generally, growth rate were faster in combined algae than in single algae diets. Specific growth rate (SGR) and relative weight gain (RWG) of sea cucumber fed the combined diet C. indica and C. racemosa (0.7%d^-1 and 5.9 %w^-1 respectively) were significantly higher than that of sea cucumber fed the other diets (P<0.05). The lowest SGR and relative weight gain (RWG) were observed in sea cucumber fed the J. rubens diet. The highest value of ammonia-nitrogen production was 1.6 mg/L in H. impatiens fed J. rubens diet but the lowest value was 0.56 mg/L in C. indica and C. racemosa diet. Therefore, this study indicates that C. indica and C. racemosa are optimum seaweeds for use in the culture of the commercially valuable sea cucumber H. impatiens.