In recent decades, English has been more and more important in Vietnam. The importance of English is not only in how many people speak it but also in what it is used for. Beside the native language is popularly used in all fields of the society, English is now widely known as the major language of intercommunication, international commerce and business, science and technology and so on. Thus, people with good English proficiency are extremely needed in any fields of society. As a result, there has been a positive trend of teaching and learning English across the country. People, from children to adults, learn English with different purposes. Children learn English because of the requirement of their parents and school. Students learn English to pass the exams, to study abroad or to find a good job in the future. Adults learn English in order to be able to communicate with foreigners or do business. In general, despite deriving from different purposes, every one wants to turn English to become their own instrument in their lives. In the process of teaching and learning English, there are many factors affecting the success of language learners such as aptitude, age, personality, motivation and so on, among which motivation plays an important role. Researchers on motivation have pointed out that learners who are highly motivated can learn a foreign language better than those who are not and vice versa. This is true for both children and adult learners. With 5 years of experience in teaching English at high school, I have realized that motivation is one of the key factors that determine students’ success or failure in language learning. For teaching and learning speaking skill, the great impact of motivation is not an exception. It is undeniable that if the students are motivated, especially from the warm- up stage, their speaking will be completed more successful and their difficulties in speaking will no longer exist. This is the reason why I choose studying on factors affecting motivation in speaking English of grade 10 students is the topic for my minor thesis. This study will examine types of motivation that students have in speaking and point out some factors affected their motivation to speak. It also investigates the activities and techniques applied by teachers, students’ preferences and demands, and some difficulties teachers faced in teaching speaking. The researcher hopes that this study will figure out a concrete picture of motivation in speaking English of grade 10 students at Yendinh 1 high school and it will be of help for teachers who want to increase students’ motivation in speaking English learning.