The present investigation entitled “Biology and Morphometric Characteristics of Bactrocera dorsalis (Hendel) on Mango fruit at room temperature.”. The experiments were undertaken at the Department of Agricultural Entomology, College of Agriculture, SVPUA&T Meerut, Uttar Pradesh. (India). Morphometric study exposed that the size of egg, such as length of egg, varied from 0.5 to 0.6 mm with mean and standard deviation of 0.53±0.02 mm and width 0.1 to 0.3 mm with mean and standard deviation 0.18±0.01 mm, respectively. The size of pre-pupae varied from 2 to 3 mm as average and standard deviation 2.81±0.08 mm and Width varied from 2 to 4 mm with average and standard deviation 9.96±0.30 mm, respectively. The length of female of Bactrocera dorsalis varied from 8 to 9 mm (8.69±0.26 mm) and width 12 to 13 mm (12.59±0.38 mm). The mature larvae of 3rd instar was slightly curved in position, became slothful and stopped feeding and remain inactive for different activities except metabolically. The female length varied from 7 to 8 mm (7.69±0.23 mm) and width 9 to 11 mm with average (8.49±0.25 mm), respectively.