The aim of this research was to assess the effect of age and body weight on semen quality. The material used was secondary data of 50 Bali Bull from 2012 to 2018 which were grouped as follows. Age 2–4 years: body weight (BW) was low (260-408 kg), medium (409-557 kg) and high (558-706 kg). Age 5–7 years: BW was low (314-470 kg), medium (471-627 kg) and high (628-784 kg). Age 8-10 years: BW was low (481-580 kg), medium (581-680 kg) and high (681-780 kg). The method used in this research is a case study. The obtained data was analyzed by using Nested Completely Randomized Design. The results showed that the older the Bali bull, the volume and individual motility increased (p<0.05) but sperm concentration decreased (p<0.05). Age 2-4 years: BW significantly affected (p<0.05) the volume, sperm concentration and individual motility. Age 5-7 years: BW significantly affected (p<0.05) the volume and individual motility, but not significantly (p>0.05) sperm concentration. Age 8-10 years: BW significantly affected (p<0.05) the volume, sperm concentration and individual motility. The research concluded that the selection of Bali cattle to obtain good quality of semen production should consider the body weight.
 Keywords: Age, body weight, semen quality, semen production, Bali bull