This research aimed to investigate second language learners' motivation and learning of English and the ways in which the teachers supported the students' motivation and learning in natural classroom settings. Based on Self-Determination Theory (SDT), questionnaires were developed and data were collected from students and their teachers in twelve English language classrooms around Thailand. In addition, each lesson was observed by two observers. The data were triangulated and used to describe the students' motivation and learning and the teacher's motivational strategies in each class. The findings showed that most students had a relatively high level of motivation and many reported having internal interests in learning English; however, the level of learning was not assessed to be as high. Furthermore, a few students in almost every class showed a lack of motivation. The teachers were found to employ a variety of motivational strategies, including autonomy-support and controlling styles. While autonomy controlling strategies were commonly used in these classes, autonomy-support strategies were found only in highly motivated and high performing classrooms. The findings from this study suggest the use of strategies that do not only initialize but also nurture students' internal motivation in order to enhance sustainable learning of English in and outside the classroom; therefore, research on how motivation theories are deployed in teacher education programs should be further undertaken.