Abstract Objective High rates of concussion in sex-comparable sports have been reported at the high school (HS), however, research examining concussion rates and time loss, in middle school (MS) sports is limited; therefore, we investigated concussion rates and time loss (TL) in sex-comparable MS sports. Methods Concussion and athlete exposure (AE) data was collected for all MS sponsored events in a metropolitan public-school division between 2015/16–2019/20. AE was defined as one athlete participating in one sport-event. TL was defined as the number of days between the injury and return to sport dates. Injury rates (IR) per 1000 AEs with 95% confidence intervals (CI) were calculated for sex-comparable sports (baseball/softball, basketball, soccer, & track). Injury rate ratios (IRR) with 95% CIs were compared IR between sexes. CIs excluding 1.0 were considered significant. A Mann–Whitney U test compared mean TL between sexes. Results 76 concussions (IR = 0.35/1000AEs, 95%CI: 0.27–0.43) occurred across 215,074 AEs. Girls had a higher IR (0.48, 95%CI: 0.35–0.62, n = 52) than boys (0.22, 95%CI: 0.13–0.31, n = 24; IRR:2.18, 95%CI:1.34–3.53). Girls had a greater mean TL (20.27 ± 16.96 days) than boys (13.67 ± 5.66 days, U = 282.5, p = 0.04). Conclusions Within sex-comparable sports, girls had nearly twice the IR, and took nearly 7 days longer to recover than boys. IR differences between sexes in MS and HS athletes were consistent, however MS girls needed nearly one-week longer to recover than HS girls, while MS and HS boys were similar. Further inquiry into MS sport concussion rates, sex differences, and subsequent TL is warranted.