Information on health of fish populations and sexual maturity is useful in formulating fisheries management regulations. There is little such information on fish species of upper Tana River basin of Mt. Kenya. Therefore, a study was conducted to estimate condition factor, length-weight relationship, sexual maturity and length at 50% maturity of Labeobarbus tanensis during March - August 2020. Fish were caught in River Kathita and in adjacent four dams on upper Tana River using electrofishing equipment and gillnets respectively. Specimen of L. tanensis were sorted from the catch and lengths measured to the nearest 0.1 cm TL using a measuring board and weights to the nearest gram using a weighing balance. Specimens were dissected to reveal gonads which were further dissected to evaluate the sexual maturity stages of eggs on a 1 to 6 scale (Witte & Vandensen, 1995). Estimated condition factor was greater than 1 indicating that the fish populations were healthy. Smallest mature male and female were 12.0 and 12.89 cm TL respectively. Length at 50% maturity for males and females were 13.9 and 14.9 cm TL respectively. Over 90% of mature fish were caught in Kathita River and few in dams. Length-weight relationship for both sexes are as follows: Females: Log W = 3.154 log TL - 2.104; R2 = 0.958. Males: log W = 3.184 log TL - 2.125; R2=0.960. Information obtained will be useful in formulating mesh-size regulations for sustainable exploitation of the fish.