Abstarct: Discourse markers (DMs) play a vital role in establishing textual cohesion and rhetorical coherence in second language (L2) academic writing. However, English as a Foreign Language (EFL) learners frequently struggle with the appropriate selection, positioning, and syntactic integration of connectors, often drawing heavily on first language (L1) rhetorical habits. This study investigates the patterns, frequency, functional distribution, and misuse of discourse markers in the argumentative writing of Iraqi 5th Scientific Grade EFL learners, examining the extent to which L1 Arabic discourse patterns transfer into L2 English text production. Employing a mixed-methods design, the study utilized a parallel writing task setup administered to participants at Alnajaf School for Distinguished Students. Learners completed two 60-minute argumentative essays (250–350 words)—one in L1 Arabic and one in L2 English—on a parallel prompt regarding the impact of technology. Quantitative data were analyzed through a functional taxonomy focusing on additive, adversative, causal, and sequential markers, combined with an essay coherence scoring rubric. Qualitative insights were gathered through retrospective stimulated recall interviews to explore learners' underlying cognitive and cross-linguistic decision-making processes. Quantitative findings revealed a heavy over-reliance on high-frequency additive and causal markers, with a prominent overextension of sentence-initial and directly traceable to L1 transfer from the Arabic continuative connector wa-. Adversative and sequential markers exhibited higher rates of positional, punctuation, and contextual misuses, such as the improper placement and framing of however. Qualitative interview protocols confirmed that students frequently conceptualize ideas in L1 Arabic prior to English translation, projecting Arabic cohesive strategies onto L2 structures without complete awareness of L2 pragmatic and syntactic constraints. This cross-linguistic transfer frequently resulted in mechanical over-cohesion rather than authentic textual coherence. The study concludes with pedagogical recommendations for Iraqi secondary EFL writing instruction, emphasizing the necessity of explicit contrastive instruction that moves beyond memorized vocabulary lists to address the functional, positional, and rhetorical nuances of discourse markers.