In this study the researcher tried to investigate whether tasks have any effect on "adjective" learning or not. To achieve this purpose, the following research question was set forth by the researcher: "Does using 'authentic task' have significant effect on 'adjective' learning?" A proficiency test was administered to minimize the individual difference among learners and to make certain the homogeneity of them. Then, before starting the treatment, a vocabulary test was given to the learners to see if the knowledge of vocabulary items already exists among participants or not. After the test, the known "words" even by one learner were omitted from the whole study. Subsequently, each group received an especial kind of treatment for 12 sessions. At the end, a multiple choice vocabulary post-test similar to the pre-test was administered. To analyze the findings of the study, SPSS (Statistical Package for social science) was utilized and the obtained results indicated that using "authentic tasks" contributed to the enhancement of "adjective" learning.