Demotivating factors are one of the sources that can reduce students' motivation toward language learning. This study investigated language learning demotivating factors among high school EFL students. It also explored the educational implications and recommendations for promoting EFL students' motivation from teachers' perspectives. A total of 365 Saudi high school EFL students and 18 secondary English language teachers from six public schools participated in the study. The data of the study were collected via two research instruments: a questionnaire and semi-structured interviews with students and teachers. The results revealed that subject-related and teacher-related demotivating factors were the most reported demotivating factors for Saudi high school EFL students. The results also showed that lack of interesting topics, lack of activities for practicing English, overemphasis on grammar, and incompetence of teachers were the most demotivating factors for EFL students toward English learning. Moreover, several recommendations for promoting students' motivation have been suggested by teachers such as technology use, extrinsic motivation and encouragement, and competitive and collaborative work.