Studies on learner demotivation has attracted the attention of second language (L2) researchers and scholars worldwide in recent years. In this paper, L2 demotivation is defined as external and internal influences which can lead to the diminishing motivation to study the target language. This paper further identifies and discusses significant influences in the form of teacher- and learner-related factors that affect learner demotivation. For teacher-related influences, inappropriate teaching styles and attitudes, poor teaching quality as well as teacher demotivation have been cited by several studies as key factors of learner demotivation. Learner demotivation can also be affected by learner-related influences arising mainly from intrinsic issues such as low self-esteem or poor self-worth. Suggestions for pedagogical implications include the enhancement of teachers' professional development, the use of 5Ts (Teacher, Teaching Methodology, Text, Task and Test), as well as imparting students' coping strategies for self-regulation. Finally, we suggest that future studies on demotivation could explore less commonly applied theories and research methods and expand demotivation research to include older L2 learners.