This study conducted two surveys in 26 selected stations between May and September 2021 in Wangsukcheon, a tributary of the Nakdonggang, to determine the characteristics of fish communities and the health of the river's aquatic ecosystem. The number of fish collected during the survey period was 6,618 individuals from 10 families and 36 species. The dominant species among the collected species was Zacco platypus (relative abundance of 36.7%), followed by the subdominant species Rhynchocypris oxycephalus (20.3%), Zacco koreanus (19.1%), Hemibarbus labeo (4.4%), Rhinogobius brunneus (3.1%), Pungtungia herzi (2.1%), Acheilognathus lanceolata intermedia (1.9%), Carassius auratus (1.6%), and Hemibarbus longirostris (1.5%). This study identified one legally protected species, Korean trout (Cottus koreanus), which is designated as endangered wildlife (class II) by the Ministry of Environment, 12 species of Korean endemics, resulting in an endemism rate of 33.3%, as well as one migratory (diadromous) species, Plecoglossus altivelis, one climate-sensitive species, C. koreanus, and one ecologically disturbing exotic species, Micropterus salmoides. Analysis of cluster characteristics revealed that the distribution of species was primarily influenced by longitudinal environmental factors such as water width, altitude, stream order, and bed slope from upstream to downstream. Secondary influences included riverbed types (boulder, cobble, pebble, or sand), water quality, and the presence of weirs (fishways) in the stream. Community analysis showed a decrease in the dominance index, while the diversity and abundance indices tended to increase from upstream to downstream. The cluster structure was divided into three groups: uppermost, upper-mid, and lower. The health of the river ecosystem and water quality were generally good, although they tended to deteriorate from upstream to downstream. Specifically, the fish assessment index (FAI) was rated as very good (A) for nine stations, good (B) for eight stations, normal (C) for eight stations, and poor (D) for one station. Water quality was rated as good (Ib) for three stations, slightly good (II) for two stations, and normal (III) for two stations. Disturbance factors such as river works, low fishway installation rates, water pollution, and the habitat of ecologically disturbing species (M. salmoides) were identified. Therefore, reckless river construction should be avoided to ensure a stable habitat for fish in Wangsukcheon Stream. It is recommended that fishways be installed to facilitate fish movement, and management measures should be implemented to improve water quality downstream and prevent the spread of ecological disturbance species (M. salmoides).