This empirical study attempts to examine the use of cohesive devices in the written discourse of EFL undergraduate students and seeks to find how the use of incorrect and repetitive cohesive ties affects the effectiveness of academic writing. Halliday and Hasan's (1976) list of cohesive devices was employed to analyze the cohesion in the descriptive, process analysis, and argumentative essay writing of the Saudi students. The researchers investigated the quantity of various cohesive ties and its effect and relation on the quality of writing. The data were collected from fifteen EFL students of the second year pursuing B.A. For data collection, the instruments were five descriptive, five narrative, and five argumentative essays. These essays were analyzed in terms of grammatical cohesion-reference, substitution, ellipsis, lexical-reiteration, collocation, and lexico-grammatical cohesion-conjunction. The results indicated that learners made ample use of cohesive ties with the overuse of reference particularly pronouns and reiteration, especially repetition of words while ignoring or underusing other cohesive devices, such as substitution, ellipsis, synonymy, antonymy, collocation, and conjunction, thereby implying the inappropriate use of linkers in their writing. Sometimes they provide a linker that is not needed, and other times, they use them in abundance without being required in the text. The inappropriate occurrence and excessive frequency of pronouns and repetition of the same lexical items lead to non-cohesive writing affecting its structure and meaning. The researchers recommended some suggestions based on the findings to imply in the pedagogy of writing.