This research aimed to find out what teaching skills that should be mastered as perceived by pre-service teachers as well as internal and external factors which trigger pre-service teachers to improve teaching skills. This research was conducted in one private university of Yogyakarta. This research involved three pre-service teachers as participants. This research employed a qualitative method and used descriptive qualitative as the research design. This research used interview to gather the data and used coding to analyze the data. The findings showed that there were three main categories of skills should be mastered as perceived by pre-service teachers namely skills before teaching, whilst teaching and after teaching. Skills before teaching include skill to make a lesson plan, prepare teaching media, prepare teaching material, improve English language mastery, and improve teaching technique. Skills whilst teaching include skill to manage time and manage the classroom. Then, skills after teaching include skill to evaluate students’ understanding and skill to evaluate the teaching. Then, there are four internal factors and seven external factors trigger them to improve teaching skills. Internal factors include interest to do teaching activity, willingness to get a job, willingness to make students understand, willingness to improve confidence, and willingness to apply teaching theory. The external factors are students' good habit, good school facility, technology development, in-service teacher’s feedback, school regulation, preparation for scholarship and requirement to make a detail lesson plan.