The growth of the juveniles of Penaeus monodon (Fabricius) was studied for a period of 77 days under light and dark conditions in the laboratory. Length and weight relation showed that the weight of the juveniles increased more rapidly under the dark condition as compared to the light condition. The exponent values (b) obtained for dark condition was higher (b=3.99; r=0.99) as compared to light condition (b=1.52; r=0.92). The maximum growth in weight was observed between 7th and 10th weeks under dark condition whereas, between 7th and 9th weeks under light condition. The growth pattern with respect to weight fitted well with von Bertalanffy’s growth equation and showed observed values closed to calculated values.