This paper entitled “The Competency-Based Approach and the EFL Learner: An Analysis of Common Grammatical Errors of Terminale Students in GHS Biyem-Assi, College Vogt sets out to examine the grammatical errors of Terminale EFL learners of some selected schools in Yaounde, within the CBA teaching/learning context. The Error Analysis perspective to language analysis was adopted for this article. Data was collected from 100 essays and also through a teacher questionnaire and an interview. The 100 participants were asked to write an essay on specific topics. Errors from the essays were identified and classified under various categories such as prepositions, nouns and determiners. A questionnaire of 15 questions was administered to 10 teachers to seek their opinions on the sources of learners’ errors. Eight teachers were interviewed. The results revealed so many grammatical and structural deviations in EFL students’ writings even though exposed to CBA. Most of the errors were noticeable in the learners’ use of verbs. It was realised that EFL students get to secondary school with very little knowledge of the English language use and this affects their writings. The poor performance of EFL Learners in grammar even though being exposed to the CBA Teaching/Learning method can be attributed to the fact that CBA was this year at its first implementation in Terminales classes and no precise course book or programme is designed to fit the teaching/learning needs.