The study contributes to research on the development of the heritage language after return to the country of origin and examines whether the ultimate attainment of the heritage grammar after many years of residing in the country of origin brings returnees to a level compatible with that of monolinguals. We focus on the production and perception of evidentiality markers in the heritage Turkish of Turkish-German bilinguals who returned to Turkey after finishing a German high school and have been residing in Turkey for more than 11 years. Two production tasks (a narrative task and a discourse completion task), as well as a grammaticality judgement task were used in the study. The data analysis revealed that the production and perception of evidentiality by the returnee participants diverged from those of the monolingual control group. The divergence manifested itself in ungrammatical uses of evidentiality markers in the context of the indirect evidentiality and less sensitivity to grammatical and ungrammatical items comprising direct and indirect evidentiality markers. The findings of the study suggest that after many years of residing in Turkey the language behaviour of the returnee participants still possesses features that are typical for heritage speakers.