This study investigates the teaching of vocabulary in ESP courses within the paradigm of task-based language teaching, concentrating on Persian literature students at Birjand University in Iran. Two homogenous groups of students who were taking their ESP courses participated in the study as a control and an experimental group. A teacher-made test of technical vocabulary knowledge was administered as the pre-test. Vocabularies in the control group were taught using a traditional approach, whereas in the experimental group, technical vocabularies were taught on the basis of task-based approach. At the end of the semester, a post-test was given to the students to determine the influence of the treatment on the experimental group. Data analysis showed that the task-based approach was more effective in teaching technical vocabularies compared to the traditional one. Furthermore, the results showed that in the experimental group the male learners outperformed the female learners.