This study investigates Mandarin Chinese learners' motivation in a Content and Language Integrated Learning (CLIL) program in a British secondary school from the perspective of learning environment, learner engagement, and learner identities. Fifteen pupils who are learning Chinese as a foreign language (CFL) have been interviewed individually or in a focus group. The results indicate that the context of L2 learning and pupils' learning experience contribute to their sustained motivation. More specifically, the nature of the CLIL subjects, teachers and their teaching methods, peers, tasks, and examinations all play an important role in motivating or demotivating students. Pedagogical implications have been discussed with suggestions for maintaining students' motivation in CLIL programs. This article fills the gap in the field of motivational study by bridging the learning of CFL and the CLIL context.