Background and Purpose: Demotivation has been acknowledged as a significant factor in the decrease of student enrolment and the increase in student attrition rates within the domain of Mandarin as a foreign language (MFL) learning. This study seeks to identify the causes of demotivation among learners of MFL at a public tertiary institution in Malaysia. Methodology: The study's sample consisted of 72 undergraduate students enrolled in an introductory-level MFL elective course. Data were collected using online questionnaires at the end of the academic semester. The online questionnaire consisted of two sections: the first focused on the demographic information of the participants, and the second contained open-ended questions. Participants were asked to characterize the learning experience that (1) negatively impacted their motivation and (2) caused them to feel frustrated or want to quit their MFL studies. The data was subjected to thematic analysis, and the themes from the responses were identified and categorized. Findings: The factors that contribute to demotivation can be classified into two categories: internal and external. Internal categories include psychological states such as anxiety and boredom. In contrast, external categories include test performance, course content, workload, and significant others (teachers and peers). External factors, particularly test performance, course content, and workload, have a greater impact on the demotivation of MFL learners compared to internal factors. The most frequently cited factor is test performance, primarily due to the difficulty of learning course content, particularly Chinese characters. One-third of the students in this study spent more than three hours per week on MFL learning outside of class. However, many students struggle to manage their Mandarin study time due to other academic or extracurricular obligations. Contributions: The current research offers additional insights into the nature and characteristics of demotivation in foreign language learning, specifically among non-native Mandarin learners with little or no prior knowledge, in the context of MFL as an elective course. Keywords: Demotivation, LOTE, Mandarin as a foreign language, Malaysian tertiary institution, elective. Cite as: Paee, R., Lam, K. C, Kuan, W. L, & Kopli, N. H. (2024). Demotivation in Mandarin as a foreign language among Malaysian tertiary students. Journal of Nusantara Studies, 9(2), 40-56. http://dx.doi.org/10.24200/jonus.vol9iss2pp40-56