This study aims to analyze and describe the forms of
Madurese language interference on the pronunciation skills
of EFL students at SMP Negeri 1 Randuagung. The study
uses a descriptive qualitative method with data collection
techniques through observation, interviews, and documentation. The results show that Madurese language
interference appears predominantly in the phonological
aspect, especially in the form of consonant substitution (/v/ to /f/, /ʃ/ to /s/, and /θ/ to /t/), difficulty in distinguishing long and short vowels, omission of final consonants, rigid and monotonous intonation. This pattern of errors indicates phonological transfer from the mother tongue, which affects students' English pronunciation. These findings support the theory of language transfer, which states that the sound system of the first language influences the production of sounds in the second language. Pedagogically, these research results emphasize the importance of phonetic awareness-based pronunciation learning strategies and sound contrast exercises to reduce the influence of the mother tongue and improve students' pronunciation accuracy.