<![CDATA[The increasing number of international students learning Indonesian as a Foreign Language (BIPA) highlights the importance of understanding the syntactic difficulties they encounter during language acquisition. This study aimed to identify and classify the types of syntactic errors produced by beginner-level international students at the BIPA Program of Universitas Muhammadiyah Kendari and to analyze the factors underlying the occurrence of those errors. A descriptive qualitative research design was employed involving six international students from Madagascar, Kenya, China, and Palestine. Data were collected through essay-writing tasks and semi-structured interviews. The written data were analyzed using Chaer's (2015) syntactic framework, while the interview data were analyzed thematically and interpreted using Error Analysis (Ellis, 2015) and Interlanguage Theory (Selinker, 1972). The findings identified four categories of syntactic errors: Word Relations Errors, Phrase Formation Errors, Clause Construction Errors, and Sentence Construction Errors, with Sentence Construction Errors occurring most frequently. The interview analysis revealed three factors underlying these errors, namely language transfer during writing, limited Indonesian linguistic competence, and the gradual development of Indonesian language proficiency. The findings indicate that syntactic errors represent learners' developing interlanguage rather than merely inadequate language competence. This study contributes to BIPA research by providing a systematic classification of syntactic errors and highlighting the cognitive and linguistic factors underlying their occurrence, offering practical implications for Indonesian language instruction for foreign learners. Keywords: BIPA; Indonesian as a Foreign Language; syntactic errors; error analysis; interlanguage]]>
