(MA Linguistics)The main objective of this study was to investigate the effective use of cohesive devices in essay writing by undergraduate students particularly the second year students of the State University of Zanzibar (SUZA). The objectives of this study were: To examine the use of CDs by SUZA students in writing essays, to analyze appropriate and inappropriate use of Cohesive Devices in students‟ essays and to propose the techniques for improving students‟ ability in using cohesive devices in producing coherent essays. The study used simple descriptive analysis and employed qualitative approach. Data were collected through documentary review (Students‟ essays), interview and focused group discussion. The target population comprised of University students from State University of Zanzibar and their linguistics lecturers. The results from students‟ essays showed that repetition, reference and conjunction were the mostly used cohesive devices, while synonym, hyponym and antonym were the least used devices. However, some inappropriate uses of cohesive devices were also easily noticed. In short, some cohesive devices were widely used but inappropriately, while some of them were less used but appropriately. The findings also revealed that students‟ writing demonstrated some weakness on the use of these devices as they made some errors in the application of these ties, the reasons behind were connected with lack of knowledge on the use of CDs as it led students to use these devices inappropriately, also its effect was seen to be influenced by mother tongue something which led to students‟ transferring the rule from their mother tongue to the target language. Moreover, it was revealed that limited vocabulary made the students to base on redundant repetition.