Abstarct: Teachers' motivation plays a crucial role in their career. Identifying the factors hindering ideal efficiency in teaching English as a foreign language (EFL) and also factors improving EFL teachers’ motivation help policymakers, instructional managers, and curriculum developers solve EFL teachers’ demotivation and promote efficient teaching. Due to paucity of research on Iranian EFL teachers’ motivation in the two contexts of junior high schools and private institutes, this study was conducted to assess their motivation in both contexts through analyzing interview results. A qualitative design was adopted in collecting and analyzing data, using constructive grounded theory approach. To this end, a total of 20 teachers, 10 teachers teaching English in junior high schools and 10 teachers in private institutes, were interviewed to discover their motivational factors and also to identify their perceptions regarding various factors affecting teacher motivation. To do so, the researcher prepared a list of 6 questions that addressed the motivational factors among EFL teachers. The researcher transcribed the interviews, coded the data, and arranged them into rising codes till data saturation. The results revealed that although there is a significant difference in the motivation of the two groups of EFL teachers, both groups suffer from some demotivational factors. The findings also suggested that the factors identified as influencing teachers’ motivation were of diverse internal and external types ranging from personal life, salary, students’ behaviors, and promotion affairs, to the evaluation system.