This study examined the incidental acquisition of English prepositions by Arabic-speaking English as a foreign language (EFL) learners. Employing reading comprehension exercises as a treatment, we adopted the experimental design of a pre- and post-test to determine the effectiveness of the treatment on the participants' incidental acquisition of English prepositions. For the purpose of the study, we divided the participants into a treatment group, who engaged in reading comprehension exercises for one academic term, and a control group, who did not. We used a multiple-choice test and a fill-in-the-blank test to measure the participants' receptive and productive knowledge of English prepositions, respectively. We also conducted an introspective session with the treatment group following the administration of the post-tests to determine the areas of difficulty. The results of the study mainly indicated that reading accompanied by exercises resulted in better incidental gains in the acquisition of English prepositions, especially on the multiple-choice test. The study concludes with recommendations for further research.