Freshwater streams on oceanic islands serve critical ecological and economic functions. However, these are underrepresented in assessments of pollution from contaminants of emerging concern (CEC). Furthermore, freshwater streams and their endemic fauna often have characteristics that are distinct from those of continental streams and model species, calling extrapolations from studies of such systems into question for island streams. In the current study, we assessed the presence of CEC across three sampling events and five freshwater streams on the Island of Hawai’i. We also exposed juveniles of the native fish species Sicyopterus stimpsoni to a mixture of commonly co-occurring CEC for 96 h in static renewal experiments, testing for impacts of CEC in two ecologically relevant assays of functional performance. CEC from multiple sources were ubiquitous in Hawaiian streams, including human-use pharmaceuticals, agricultural herbicides, and industrial runoff. Concentrations of CEC were comparable to published studies from continental streams, exceeding total concentrations of 1000 ng/L for the eight quantified CEC in four samples, and approaching 2500 ng/L in one sample. Effects on exposed fish were subtle and limited to treatments with higher CEC concentrations but indicated potential impacts of CEC on locomotor performance. These results indicate that Hawaiian streams follow a global trend of widespread freshwater pollution by CEC that are accompanied by subtle effects on native fish species and highlight the need for the inclusion of endemic species and ecologically relevant assays when assessing the effects of contaminants in island habitats.