This study investigated the effects of teaching vocabulary through the lexical instructional approach in EFL intermediate level students. Ninety-five (95) students participated in a non-equivalent pre-test-post-test quasi-experimental design study. The participants were given vocabulary competence pre-test in order to check their homogeneity in terms of their vocabulary knowledge. Then, following the similitude of the results they scored, the participants were randomly assigned as experimental group and the control group. For sixteen (16) weeks, the experimental group was taught by providing students with chunks and/or collocates of words through using collocation dictionaries, concordance programs, chunk-for-chunk translation activities, and corpus-based activities etc. Whereas, the control group was taught the new words in isolation with conventional teaching techniques; for example, translation at single word level, synonyms, antonyms, and definitions. After the instructional intervention, both groups participated in a vocabulary competence post-test. The Statistical Package for Social Science (SPSS) software version 22 was employed to analyse the results. In this regard, an independent Samples T-test was run and the findings of the study showed that the experimental group outperformed the control group in the post-test which implies that teaching vocabulary with a lexically-based instruction can improve EFL learners' vocabulary competence or knowledge. Furthermore, the study results suggest that the lexical instructional approach should be the focus of future experimental research.