This study aimed to assess the extent of compatibility between materials design, assessment methods, and Competence-Based Language Teaching (CBLT) in Tanzania. It also dealt with examining the pertinent challenges that English Language teachers encounter in adopting authentic materials and assessment methods in their classrooms. This study employed both quantitative and qualitative research designs. The data for the study were collected by using survey questionnaire, face-to-face interviews, and documentary review. A total of 42 informants: school teachers, TIE, and NECTA officers, were involved in soliciting the necessary information with regard to the research problem. The findings indicate that there is minimal compatibility between materials design, assessment methods, and CBLT. The materials adopted in schools do not match with the requirements of the curriculum, also the assessment methods have not changed with the adoption of a new curriculum. The findings further revealed that there are pertinent challenges facing teachers to the extent that they impede a smooth implementation of some aspects of the curriculum. These challenges include: Huge classes, problem of funding for teaching resources, inherent wrong assumption about authentic assessment methods held by English teachers, lack of knowledge about the curriculum and heavy workload. To curb these challenges, a number of recommendations have been given by the study; one of which being the need for the government to develop partnership between universities, teachers’ colleges, and schools so as to share knowledge and disseminate the necessary information and skills for the introduced innovations in the curriculum. In order to have quality teaching/learning materials, TIE should be given a fundamental support in terms of funds so as to develop quality textbooks relevant to the curriculum instead of leaving this noble task to private authors. Also the study recommends that NECTA should adhere to what the CBLT requires in assessing learners’ achievement. Lastly, the study recommends that English language teachers should employ their professional creativity in dealing with the observed challenges instead of throwing blames to other stakeholders.