<p>For Chinese adolescents, a stronger sense of school belonging has been linked to higher academic achievement. Yet, sense of belonging has typically been analyzed only as an individual-level construct, even though its effects may depend on how their sense of belonging stands relative to their peers. This study introduces the concept of <i>relative sense of belonging</i>—how a student’s sense of belonging compares to the average belonging level in their school—and examines its association with adolescents’ academic performance, overall and by gender subgroups. The sample consisted of Chinese adolescents who participated in the 2018 Program for International Student Assessment (<i>N</i> = 12,058, <i>M</i>_age= 15.8; <i>SD</i> = 0.30, 48% female). Results based on two-level hierarchical linear models show that higher relative sense of belonging significantly predicted higher achievement across a broad range of academic domains—math, reading, and science—for students, overall, and in reading and science for boys. However, these positive associations were not observed among girls, suggesting possible gender differences in how relative sense of belonging relates to academic outcomes. By focusing on relative sense of belonging, this study highlights that students’ standing compared with their peers’ sense of belonging can play an important role in academic achievement.</p>