This study investigated the way in which American university students learning Arabic as a foreign language in the United States developed the ability to make and modify requests both internally, through an addition of mitigating or aggravating modality markers, and externally, via supportive moves before or after the main request in formal and informal situations. Data were gathered from spoken discourse completion tasks for 56 university students from four different proficiency levels. While previous studies showed that learners at lower proficiency levels relied heavily on politeness markers, lower-proficiency students in this study most frequently used grounders. Also in contrast to previous studies, the ways in which advanced learners mitigated their requests diverged from those used by Arabic native speakers. Pedagogical implications are discussed.