The present research work entitled “Correlation of testicular ultrasonography, testicular biometry, serum testosterone levels and seminal attributes in pre- and post-pubertal age for breeding soundness evaluation in Osmanabadi bucks” was undertaken in 18 healthy Osmanabadi bucks from the Instructional Livestock Farm Complex, Bombay Veterinary College, Mumbai, Maharashtra. The body weight (kg), scrotal circumference (cm) and testicular biometry (cm) of post-weaning 18 Osmanabadi male kids was recorded every 15 days from weaning, i.e., 120?±?10 days along with serum testosterone (ng/ml) by radioimmunoassay method at monthly intervals for the next 6 months. Semen was collected six times on the seventh month onward during post-pubertal age at 15-day interval from 18 bucks. The semen was evaluated for macroscopic and microscopic tests. The body weight increased from 14.45?±?0.67 to 19.57?±?0.70 kg from four to nine and a half months of age. The average daily body weight gain was 31.27 g. Maximum body weight gain was 01.19?±?0.16 kg from 5 to 6 followed by 01.15?±?0.16 kg from 4 to 5 months of age. The scrotal circumference increased from 17.22?±?0.56 to 19.03?±?0.55 cm from four to nine and a half months of age with maximum increased between 4 and 5 followed by 6 and 7 months of age. The testicular length, width and thickness of right and left testicles were recorded by ultrasonography method. There was increase in mean right and left testicular length, width and thickness from 5.25?±?0.19 to 5.84?±?0.18 and 5.49?±?0.21 to 6.16?±?0.20; 2.99?±?0.12 to 3.32?±?0.12 and 3.10?±?0.13 to 3.44?±?0.12 and 2.97?±?0.12 to 3.16?±?0.12 and 3.06?±?0.12 to 3.31?±?0.11 cm, respectively by ultrasonography, between four to nine and a half months of age. Testicular length, width and thickness gain was at maximum in 5 to 6 months of age. Left testicular length was more than the right testis. Before puberty, there was sudden gain in body weight, testicular length and width. However, scrotal circumference showed significant increase after puberty. Body weight had highest correlation with ultrasonographic left testicular thickness (r?=?1) followed by scrotal circumference, ultrasonographic right and left testicular width, left testicular length, right testicular length and thickness and least by right testicular thickness (r?=?0.95). The semen was thin to thick in consistency and average semen density was 3.10?±?0.05. Average semen volume was 0.81?±?0.02 ml, mass activity, initial motility, live and dead sperm count, abnormal sperm count and sperm concentration were 3.45?±?0.13, 76.16?±?1.16 and 75.16?±?1.28% and 24.84?±?1.28, 12.30?±?0.50% and 2631.04?±?45.74 million/ml, respectively in 18 bucks in six collection at 15 days. There was significant rise in semen volume, mass activity, initial motility and concentration at 8.5 months and live count, density at 9 months of age which indicates the age of sexual maturity is 8.5 to 9 months in Osmanabadi bucks. The body weight had highest positive correlation with mass activity (r?=?98) followed by initial motility, live sperm count and total sperm concentration, semen volume (r?=?76). The scrotal circumference had highest positive correlation with initial motility (r?=?98) followed by live sperm count, total sperm count, mass activity, semen volume (r?=?86). On the other hand, body weight and scrotal circumference were negatively correlated with abnormal and dead sperm count. The mean testosterone concentration increased from 0.02?±?0.004 to 5.75?±?0.80 ng/ml between four and half to nine and half months of age, respectively. There was significant rise (p?<?0.01) up to 1.38?±?0.28 ng/ ml at 6.5 months, i.e., age of puberty and up to 5.75?±?0.80 ng/ml at 9.5 months, i.e., age of sexual maturity. Testosterone had highest positive correlation with testicular length followed by testicular width, length, body weight and scrotal circumference, mass activity, live sperm count, initial motility, while it had highest negative correlation with dead and abnormal sperm count. From the present research work, it was concluded that the scrotal circumference, testicular length, width and thickness increased with increasing body weight. Before puberty, there was sudden gain in body weight, testicular length and width. However, scrotal circumference increased significantly at post-pubertal age. So testicular length, body weight, testicular width in pre pubertal age and scrotal circumference post-pubertal age can be used as indicator for selection of Osmanabadi bucks for breeding purpose. On the other hand, the semen parameters should consider only after 8.5 to 9 months of age for selection of Osmanabadi bucks for breeding.