It has been well learnt that a large number of Arab EFL learners encounter a considerable degree of complexity in the use of tense and aspect as fundamental components of the English language. Such a degree of difficulty is perceived and experienced by those learners at their different levels of learning English starting at the primary level up to the university level. This is what has led the researcher to carry out this research with the major aim of looking into the reasons behind the failure of such learners to handle the use of tense and aspect of English in a proper manner. The sample of this research comprised a group of students studying English as an ESP course, who were on the verge of graduation in the College of Engineering, Jazan University. The research tools used were both a test and a questionnaire. The findings of the research show that those learners encounter a great deal of complexity in the use of tense and aspect. This is clarified by means of their inability to use tense and aspect in English as correct as they should. This complexity is greater in the case of the use of the aspect. The research concludes with forwarding a number of conclusions resulting from the discussion of the results; and these conclusions are followed by a number of recommendations that can be useful for teachers, curricula designers and decision makers.