<p>The introduction of non-native fish species can substantially alter aquatic ecosystems; yet, their impact on invertebrate assemblages remains understudied. We investigated how goldfish presence influences the abundance, species richness and diversity, assemblage composition, species turnover rates, and morphological traits of Odonata nymphs in sub-Mediterranean ponds. Both Odonata species abundance and richness were higher in fishless ponds, Shannon diversity index was greater for Anisoptera, while the Dominance index was higher for Zygoptera. Species turnover rates between fishless and goldfish-occupied ponds were significantly different for Zygoptera and Anisoptera, indicating shifts in Odonata assemblages in response to goldfish presence. Morphological analysis revealed significant differences in body size between nymphs from fishless and goldfish-occupied ponds, especially in <i>Anax imperator</i>, which also displayed well-developed defensive structures in goldfish-occupied ponds, possibly as an adaptation to predation. While certain species exhibited adaptive morphological changes to withstand predation pressure, others showed differences in occurrence between fishless and goldfish-occupied ponds (e.g., <i>Cordulia aenea</i>, <i>Sympetrum sanguineum</i>, and <i>Sympetrum striolatum</i>), suggesting species-specific responses to goldfish presence. These findings underscore the ecological consequences of introducing fish species into aquatic habitats and highlight the importance of conservation efforts to protect vulnerable Odonata populations.</p>