In a globalized world, second language (L2) learning has become one of the most important aspects of education. Consequently, it is important to investigate one of the most important factors for learning a language, which is motivation. There are many studies investigating learners’ motivation; however, there are very few investigating learner L2 demotivation and demotivating factors that negatively influence learners’ progress. For this reason, this thesis aims to investigate the main demotivating factors in learning the English language among high school learners. The method of investigation included quantitative and qualitative methods, including the use of a questionnaire, an open-ended question, and interviews. The results show that learners are fully aware of the reasons why are they sometime demotivated to learn. The questionnaire showed that the teacher has the most important role in demotivation. On the other hand, the open-ended question suggested that discontent with the program and school, in general, was a major demotivating factor along with the role of the teacher. The interviews revealed that students’ perceptions of their abilities, that is, their lack of knowledge was the most frequent demotivating reason. In addition, the teacher was also cited as another important demotivating factor. In brief, this study has shown various factors which contribute to student L2 demotivation which needs to be taken into consideration by teachers, as well as policy makers.