Hydropower is crucial for meeting Ethiopia’s energy needs, but it can have ecological and socio-economic impacts if not managed properly. This study was conductedin the Tana Beles Hydropower Plant.The study aimed to assess the impact of theTana Beles Hydropower Plant on fish diversity, composition, and the socio-economic conditionof fishers. Data were collected through a combinationof field sampling, key informant interviews, focus group discussions, and questionnaires. Physico-chemical parameters were measured insitu using a portable multi-parameter device, and fishes were collectedusing gillnets of various mesh sizes.Fish species were identified using taxonomic keys, and their lengths and weights were recorded. Significant differences in physico-chemical parameters were observedbetween sampling sites across all parameters.A total of 374 fish specimenswere collected,of these 271 from upstream and 103 from downstream predominantly belonging to the cyprinidae family.Shannon diversity was higher at the upstream sites (H' = 1.66) than at the downstream (H'= 1.41), indicating moderate diversity.The species that dominated the upstream sites were Labeobarbus brevicephalus (46.0%) while, Labeobarbus beso (0.24%), was the least abundant. In contrast, Labeobarbus nedgia (42.85%) dominated the downstream sites, while Oreochromis niloticus (2.75%) was the least abundant. Length-weight relationships varied among species, Labeobarbus intermedius (upstream) and Labeobarbus nedgia (downstream) exhibiting isometric growth, while others displayed allometric. Fulton’s Condition Factor exhibited significant site-specific variation in Labeobarbus brevicephalus, but not in Labeobarbus intermedius or Labeobarbus nedgia.Females were more numerous than males.Survey responses revealed that all fishers attributed fish mortality primarily to injuries from hydropower turbines, with 63.2% also reporting increased vulnerability to predation linked to turbine infrastructure. The study recommended adopting fish-friendly designs and monitoring fish movements near intakes to ensure sustainable fish populations and ecosystem health.