In this article, we explore one aspect of language awareness that has rarely been explored--awareness (i.e. perception) of the language proficiency of the "other learner" in pair work settings. We examine how Mai, a Japanese ESL learner, perceives her peer's L2 proficiency during pair problem solving, and how her perception of learner proficiency affects the nature of peer assistance. Mai engaged in a three-stage task involving pair writing, pair noticing and individual writing with two learners whose L2 proficiency level is either higher or lower than her own. She also provided stimulated recall and was interviewed after all the tasks were completed. The findings suggest that measured proficiency difference does not necessarily affect the nature of peer assistance. Rather, how each learner perceives each other's proficiency difference, and how they interact with their peer based on the perceived proficiency level may be more significant.