The adoption of the Common European Framework of Reference (CEFR) as the benchmark against which Malaysia's English curriculum must be measured has stirred up the ESL education community, particularly the instructors, in a number of ways. However, opinions on its success and difficulties run the gamut from wholly endorsing the concept to wholly rejecting it. The objective of this review is to methodically pinpoint the problems that frequently arise when the CEFR is implemented in ESL or EFL classrooms around the world. 26 papers from the year 2018 to 2023 were extracted using two databases, Google Scholar and the Educational Resources Information Centre (ERIC), while considering inclusion and exclusion criteria. The important findings showed that the concerns about the adoption of the CEFR in ESL and EFL classrooms revolve around the teachers' factors,the challenges and practicality issues, the curricular aspects and the materials. The adoption of the CEFR in ESL/EFL classrooms was only partially successful because, despite the fact that most teachers have a positive attitude towards the adoption, issues resulting from a lack of training and appropriate materials make adoption difficult. Research on potential ways to solve the difficulties is still scarce, though. Overall, this review is deemed useful for the stakeholders around the world to have better insight on the effectiveness of the implementation if CEFR in ESL/EFL classrooms to devise remedial strategies in order to minimize the adverse effects of implementing CEFR into the nation's education system around the world and perform further researches to fulfil the inadequacy of the information of identified areas.