Lesson plan is very essential in teaching learning processes because lesson plan has a function as a teaching guideline for pre-service teachers. Having a lesson plan, pre-service teachers such as students of English Education Department of Universitas Muhammadiyah Yogyakarta find it easier to deliver the lesson in front of the students and manage the classroom. This research aimed to find out how these pre-service teachers of EED UMY implemented their lesson plan. In addition, the study was intended to investigate what the challenges were faced by these pre-service teachers in implementing the lesson plan. Descriptive qualitative was applied in this research in which the data were collected from three participants of students of EED UMY batch 2014 using observation and individual interviews. The observation was used to find out how the lesson plan was implemented in the classroom, while the individual interviews were applied to seek the challenges found by these pre-service teachers when implementing their lesson plan. Based on the observation, the findings revealed that the lesson plan designed prior to teaching practice has been generally well implemented by all participants. However, there were some aspects in the lesson plan that were not well implemented, and these aspects were further investigated in the individual interview session. Then, the data collected from the individual interviews revealed that the aspects that were not well implemented were caused by some problems. There were four problems in implementing the lesson plan faced by the participants during their teaching practice. These problems were related to forgetting the sequence activities of lesson plan, managing time, managing classroom, and lacking preparation prior to teaching practice.