This study investigated the widespread use of possessive redundancy with own in Nigerian English, particularly among tertiary students in Owerri, Imo State. Anchored on the Interlanguage theory, the study examined the influence of mother tongue, overgeneralization, and fossilization in students’ writing. A descriptive mixed-methods approach was adopted, involving 120 students drawn from five institutions, namely; Alvan Ikoku Federal University of Education, Federal University of Technology Owerri, Imo State University, Federal Polytechnic Nekede, and Imo State College of Education, Ihitte Uboma. Data were collected through essay task, and a structured questionnaire designed to elicit possessive constructions and assess students’ awareness of Standard English possessive forms. Findịngs revealed that 72.5% of students used redundant own in their essays. Mother tongue transfer was the strongest predictor of this usage, reinforced by habitual patterns of speech within the academic and social environment. The study concluded that possessive redundancy with own is a systematic feature of Nigerian English interlanguage, rather than a random grammatical error. It recommended explicit grammar instruction, contrastive analysis, and targeted correction strategies to enhance learners’ mastery of Standard English possessives, especially in formal writing contexts.
Keywords: NA