Background: Implementing Inquiry-Based Instruction (IBI) in science is a complex process demanding certain classroom conditions prepared with instructional materials to engage students in tasks, as well as adopting the social context that will shape the inquiry-based learning environment. Within this social context, teachers are the main agents who ensure successful inquiry-based implementation because their beliefs and perceptions significantly influence their practices within the classroom. Purpose: This study explored teachers' views and understandings about IBI and the factors that inhibit and promote the implementation of this teaching method. Additionally, the difference in perspectives regarding the inhibiting factors has been explored within two countries that are allocating different budgets for developing innovative educational systems to improve students' results on the international standardized tests (the United Arab Emirates and Lebanon). Results: This study identified factors such as limited ICT and lab resources, low quality of professional development, lack of time for lesson preparation, and difficulties in classroom management that complicate the process of IBI implementation in classrooms. Differences in the UAE and Lebanese teachers' perspectives were uncovered. Implications and limitations were further discussed.