In freshwater ecosystems, introducing exotic species has been a long-term problem, altering the flow of matter and energy in biotic communities. The rainbow trout (Oncorhynchus mykiss) were introduced into Colombia in the last century and has become the dominant species in freshwater aquatic ecosystems in the Andean region. The present study analyzed the impacts of rainbow trout on the food webs of the Andean streams using stomach content data and stable isotope analysis. Streams were located on the eastern flank of the central cordillera of the Colombian Andes in the Upper Magdalena River, Tolima department. These were sampled at an elevation range between 2000 and 2600 m asl with and without the presence of rainbow trout and under different types of vegetation cover (forests versus pastures and crops). Our study suggests that aquatic insects are essential in Andean food webs, where collector-gatherers and scrapers were most consumed and assimilated for native catfish and non-native rainbow trout. Furthermore, native catfish currently face double pressure when natural cover is changed and non-native species are introduced.