The present work was conducted with an aim to analyze various sexual behavior attributes for Cholistani service bulls (n = 10) being reared for AI at Semen Production Unit, Karaniwala, Bahawalpur, Pakistan and their relationship with serum testosterone levels.Bulls were divided into two equal groups (n=5 per group) viz. young(2-3 years of age) and adult (4-8 years of age).The exposure tests for assessment of sexual behavior and scoring were performed during semen collection. A total of 40 blood samples, (04 samples per animal;were 20 samples per group)were aseptically collected and used for assessment of serum testosterone concentration through automated immunoanalyser.Amongst the studied behavioral attributes,‘reaction during approach’, ‘sexual interest’ and ‘ejaculate response’ were significantly (P ≤ 0.05) higher in adults as compared to their young counterparts.Adults had a significantly (P ≤ 0.05) higher testosterone concentration (6.59 ± 0.3ng/mL) as compared to their youngcounterparts (5.34 ± 0.3ng/mL).A positive correlation between serum testosterone concentration and sexual behavior score was noticed both for young and adult bulls, though statistically non-significant (P ≥ 0.05). It is concluded thatthere is a significant difference in sexual behavior attributes and serum testosterone levels of young and adult Cholistani service bulls. This is a first attempt to analyze sexual behavioral attributes of young and adult Cholistani breeding bulls. A time-lined study need to be devised for this breed in future in order to ascertain age of puberty and allied endocrine patterns.