Breeding activities to generate seedless cultivars of fruits and vegetables have been initiated around the world due to its increased market demand and consumer acceptance. Seedless fruits and vegetables are becoming increasingly popular across the world due to their higher flesh content, enhanced sweetness and ease of consumption thanks to the lack of seeds. Polyploidy breeding is a very important aspect in horticultural crops to create genetic and morphological variation among horticultural crops. Seedless watermelons are produced through polyploidy breeding by doubling the chromosome number and crossing between normal diploid(2x) with colchicine induced tetraploids (4x).The present study was carried out in the year (May-July)2015 at the High-tech seed testing laboratory under the Department of Vegetable Science, Kerala Agriculture University, Trissur, India to differentiate between the normal diploid(2x) watermelon (var. Sugar Baby) with the yellow seedless triploid (3x) watermelon hybrid var. Swarna (KAU-CL-TETRA-1 × CL-5). The true leaf samples collected from 10 numbers of diploid (var. Sugar Baby) and 7 numbers of triploid (var. Swarna) seedlings of watermelon were taken for the study. In the present study chloroplast count and pollen grain study were undertaken as the morphological markers to carry out the experiment. The results obtained from the average chloroplast count of 10 samples of diploid (2x) sugar baby was 11.07 whereas the triploid (3x) Swarna hybrid was 12.11. The pollen grain of triploid (3x) was found to be not retained from red safranin stain colour being sterile in nature whereas the fertile pollen of diploid (2x) watermelon retained the stain colour.