<p>Wetlands provide essential ecosystem services for human well-being but despite their importance, they continue to disappear globally and with them, their biodiversity. A major threat to wetland biodiversity are biological invasions. This study therefore aims to assess the spread and ecological impacts of populations of non-native and translocated species in three wetlands (Lake Manyas, Lake Uluabat, and the Kocaçay Delta) located in the Marmara Region of Türkiye. For this, we used the recently developed Dispersal-Origin-Status-Impact (DOSI) framework, which allows for a holistic analysis of (<i>i</i>) how non-native species are dispersed, (<i>ii</i>) their origin, (<i>iii</i>) their current population status, and (<i>iv</i>) impacts on a given assessment area. Through this application, a total of 34 population-based assessments were conducted, reflecting the distribution of 18 species of fish, macroinvertebrates, and plants; seven of which being identified in all three ecosystems, two in two, and only nine in a single ecosystem. The majority of species were intentionally introduced to the region through human actions such as fisheries, bio-control, and recreational activities. <i>Carassius gibelio</i>, <i>Gambusia holbrooki</i>,<i> Physella acuta</i>, and all plants stand out as the species presenting the highest threat according to the DOSI scoring. These species’ effects, such as altering habitat structure, competing with native species and disrupting trophic networks, threaten the ecological integrity of these wetlands. Early intervention and long-term control strategies should be developed, especially for species with high impact levels.</p>