This paper offers a theoretical approach to vocabulary instruction from the evidence provided by lexical errors as the main sources of difficulty in the EFL acquisition process, it reviews previous research and from it suggests new ways of dealing with lexical errors in the classroom. Some practical implications are concluded which rely on lexical error categories identified in previous studies. Our main starting point is that lexical errors can serve as a guideline for teachers and researchers to improve vocabulary instruction. Identifying the main causes of lexical errors can help teachers understand the difficulties of their learners and assist them in planning and designing lessons and materials for the vocabulary class. Embarking from this premise, we have reviewed the main lexical error sources identified in the literature and provided some suggestions for vocabulary instruction.