Background/Context: This article addresses the classroom contextual effects of absences on student achievement. Previous research on peer effects has predominantly focused on peer socioeconomic status or classroom academic ability and its effects on classmates. However, the field has been limited by not discerning the individual-level academic effects of being in classrooms with absent peers. Purpose/Objective/Research Question/Focus of the Study: The purpose of this study is to determine the peer effects of absent students in urban elementary school classrooms. Population/Participants/Subjects: The data set is longitudinal and comprises entire populations of five elementary school cohorts within the School District of Philadelphia, for a total of 33,420 student observations. Individual student records were linked to teacher and classroom data and to census block neighborhood information. Research Design: To examine the educational effects of absent peers, this study employed an empirical specification of the education production function. The dependent variables were Stanford Achievement Test Ninth Edition (SAT9) reading and math scores. Findings: Models differentiated between unexcused and total absence measures and indicated that the peer effect of absences was driven by negative effects associated with classroom rates of unexcused absences rather with rates of total absences. These findings were obtained after controlling for student, neighborhood, teacher, and classroom characteristics. Conclusions/Recommendations: Not only are absences detrimental to the absentee, but they also have a pervasive effect on the achievement of other students in the classroom.