Purpose: This study endeavored to find out the possible relationship between reflectivity and impulsivity as cognitive learning styles and vocabulary/ grammar development as sub-skills among EFL learners. Methodology: Two intact classes of the third-grade students were selected by the researchers and Oxford Placement Test was run for homogenizing them. After that, Barrat’s (2005) Impulsive/ Reflective questionnaire was given to the participants and they had to respond the translated items in a limited time. Regarding the score scale provided by the questionnaire, the participants were labeled as reflective and impulsive ones. Next, a standard grammar/vocabulary test, extracted from their book, administered to them and the scores were recorded by the researchers. Then, the scores of the questionnaires and tests sent to SPSS software for analyzing and interpreting the data. In inferential statistics, the researchers used correlation test to examine the possible relationship between the students' learning styles and their sub-skills development. Findings: Results of the study indicated a positive relationship between the students' sub-skills achievements (vocabulary/ grammar) and their learning styles (reflectivity/ impulsivity). In other words, reflectivity and impulsivity had effect on the students' performance in sub-skills, as the reflective students presented better performance and made fewer errors than the impulsive ones in vocabulary and grammar tests. Conclusion: According to the results, it can be concluded that the higher the reflectivity of the learners is, the more successful they tend to be in such tests. It is expected that the findings of the research indicate the importance of learning styles in educational environment.
