This research uses an explanatory sequential mixed-methods approach (Creswell, 2015) to examine the relationship between the degree of alignment of components of the Libyan education system and the washback of the revised Secondary Education Certificate Examination of English (rSECEE). Washback is viewed as the influence of tests on both teaching and learning within the classroom. Some have argued (e.g., Linn, 2000; Shohamy, 1997; Tan, 2008) that lack of alignment between components of an education system may result in negative washback. Applying quantitative methods, Phase I of the study, draws on Webb's (1997) alignment model to investigate the degree of alignment between the rSECEE, Libya's English as a Foreign Language (EFL) content standards, and curriculum (i.e., the standardised textbooks in this Libyan context). Subsequently, applying qualitative methods, Phase II elicited data from three Libyan EFL teachers and their students through questionnaires, semi-structured interviews, classroom observations, and focus group interviews. Both quantitative and qualitative data were analysed, synthesized and merged into one overall interpretation of the phenomenon (Creswell, 2000). The Phase I and II results indicate that: 1) there is limited-to-no degree of alignment between the rSECEE and the EFL content standards; 2) the rSECEE does not meet Webb's (1997) comprehensive criteria; 3) rSECEE appears to have had negative washback on some teachers and their teaching, but little-to-no negative washback on other teachers; 4) rSECEE may have had negative washback on learners and their learning. Accordingly, it can be argued that the washback of rSECEE is highly complex; how teachers react is highly individual; but, teachers are the key stake-holders in mediating washback. The test design and its degree of alignment with the focal construct, the prevailing culture of learning (Cortazzi & Jin, 1992), and teachers' beliefs (Woods, 1996) seems to determine the direction, intensity (Cheng, 2005; Green, 2007, Watanabe, 1996), and magnitude of washback (Fox, 2018). This study will be of interest to test developers, administrators, and policy makers, as these stake-holders require comprehensive assessment instruments that provide valid inferences about students' achievements, without undermining learning opportunities.