© 2021, The Author(s), under exclusive licence to Springer Nature B.V. part of Springer Nature.We studied feeding behavior and prey selection of topmouth gudgeon (Pseudorasbora parva), big-scale sand smelt (Atherina boyeri) and pike-perch (Sander lucioperca) in Lake Eğirdir, the second largest freshwater lake in Turkey. Fish specimens were collected between January and August in 2010 and 2011 using gill-nets and purse seines. A total of 941 specimens were analyzed for stomach contents analysis. We expressed the importance of the food items present in their guts with the relative importance index (IRI) and estimated their diet selectivity indices with Pearre’s index. Pseudorasbora parva had a diverse diet comprising mainly Nitokra hibernica (copepod), Chydorus sphaericus, and Bosmina longirostris (cladoceran) (each, at p < 0.01), but Chironomus sp. (insect) was not a significant component of its diet (p > 0.05). Big-scale sand smelt often preferred B. longirostris, N. hibernica, and Alona quadrangularis (each at p < 0.01). Pike-perch positively, but not statistically significant, selected Atherina boyeri (p > 0.05), Carassius gibelio was not preferred by pike-perch as food item (p > 0.05). Our results indicate that invasive species altered the food chain in Lake Eğirdir. Thus, because these fish species constitute a major threat for native fish species for food and breeding grounds, extensive care should be taken to prevent invasive fish species entering lakes in Turkey.