It is imperative to understand the factor that influence teaching competency. Therefore, it is necessary to study those that have an impact on the process of acquiring teaching competency. Competent nurse teachers have an important role in the achievement of nursing students and improving the quality of nursing education. However, few researches have focused specifically on the process of acquiring teaching competency in nurse teachers and its related factors. This study as a part of more extensive research aims to explore the factors influencing acquisition of teaching competency by Iranian nurse teachers. Grounded theory was chosen as the method. Eleven teachers from three nursing schools in Tehran were recruited. Data was generated by semi structured interviews during May 2011 to March 2013 and was analyzed through using constant comparison. Three main categories were emerged including "individual characteristics" (spirituality, professional interest, ethical conducts, knowledge expansion and reflective practice), "organizational factors" (management of educational systems, solidarity culture, student characteristics) and "socio-cultural factors" (social situations, and public definition of nursing). Nurse teachers who deal peacefully with the nursing profession and colleagues are responsible and committed to acquiring teaching competency. A suitable organization in nursing educational systems that is structured and ordered also encourages a peaceful approach by nurse teachers.