1.Most naturalized and invasive alien plant species were originally introduced to regions for horticultural purposes. However, many regions now face an invasion debt from ornamental alien species, which have not yet naturalized. In this regard, climate change represents a threat as it may lower the barriers to naturalization for some ornamental alien species. Identifying those species is extremely important for anticipating impending invasions. 2.To identify predictors of naturalization, we modelled the effects of climate, nursery availability and species characteristics on the current European naturalization success of 2,073 ornamental aliens commonly planted in European gardens. We then used the resulting model together with climate projections for 2050 to forecast future naturalization risks for the 1,583 species not yet naturalized in Europe. 3.We found that non‐European naturalized range size, climatic suitability, propagule pressure, having a dioecious sexual system and plant height jointly explained current naturalization success in Europe. By 2050, naturalization probability projections increased by more than 0.1 for 41 species, and only decreased by more than 0.1 for one species. 4.Policy Implications. Using predictions based on our integrated model of alien ornamental naturalization success, we identified species with high future naturalization risk and species with high projected increases in naturalization potential in Europe under climate change. This species list allows for prioritization of monitoring and regulation of ornamental plants to mitigate the invasion debt.