Vocabulary learning is and indeed has always been one of the major con-cerns in foreign language teaching and learning. Among different aspects related to vocabulary learning and teaching, the sense relations play an important role. These relations can be found in two dimensions as the horizontal axis represents syntagmatic relations-like collocations, fixed expressions and idioms, while the vertical axis represents paradigmatic relations-such as synonyms, antonyms and hyponyms. The present study was an attempt to investigate the effects of horizontal and vertical axes on Iranian EFL learners' vocabulary learning regarding the cognitive domain levels. To this aim, 84 Iranian high school students (second grade) were chosen through a PET as the homogeneity test. These participants were also pretested through a researchers-made vocabulary test and were divided into three homogeneous groups to represent the horizontal axis group (HAG), vertical axis group (VAG), and control group. The participants went through the processes of pretesting, treatment, and posttesting. The results of data analysis (MANOVA and Independent T-test) indicated that the horizontal group significantly outperformed the vertical group on the posttest of vocabulary, while both VAG and HAG outperformed the control group. It was also revealed that the components of cognitive domain; i. e. comprehension, application, synthesis, and evaluation, except knowledge, were significantly impacted by the horizontal training method. Therefore, syntagmatic relations or horizontal axis can be considered successful in helping EFL learners improve their vocabulary. The findings are fruitful for EFL teachers and syllabus designers to develop efficient vocabulary teaching procedures.