This paper investigates the effect of daily journal writing on enhancing the listening and reading comprehension skills in a fifty-week Modern Standard Arabic course taught at the Defense Language Institute (DLI) in Monterey, California. In the field of foreign language (FL) teaching, writing has long been considered a supporting skill for reinforcing new grammatical concepts and recycling vocabulary at the sentence level, (Kepner, 2011) although some academics rule out grammar correction as ineffective in facilitating improvement in students' writing claiming that "grammar correction has no place in writing courses and should be abandoned" (Truscott, 1996, p. 328). However, researchers found other practical and effective uses for writing in improving proficiency in FL. The overall results of three Modern Standard Arabic classes, the subject of this study, were examined to establish whether the variable of journal writing is effective. Two classes out of the three were the experimental group and the third was the control group. This study examines influence of daily journal writing on the In-Course Proficiency Tests (ICPT) and the final Defense Language Proficiency Test-5 (DLPT-5) for the three classes. The findings showed that students' listening and reading comprehension skills in the six ICPT tests and final DLPT-5 test evidently correlated with the progress in students' writing skills. Statistics also revealed apparent improvement in the listening and reading comprehension skills of struggling students in the two experimental classes compared to the control class.