Low back pain (LBP) is the most common overuse musculoskeletal injury suffered by child equestrian athletes (CEA). Despite this, little is known about the risk factors related to LBP in these athletes, and very limited research has been conducted on this topic. This study was designed to investigate predictive risk factors for LBP in CEA. The purposes of this research were to determine whether anthropometric, range of motion (ROM), core endurance and sagittal spinal morphotype measures are risk factors for LBP and to establish a diagnostic cutoff value for those factors associated with LBP. Nineteen CEA between the ages of 12 and 17 years were voluntarily recruited. Potential risk factors evaluated included corporal composition, lower limb ROM, core endurance and sagittal spinal measures. Associations and predictions were calculated between these risk factors and the LBP during the last 12 months. Almost half of the CEA have suffered at least one episode of LBP. Two risk factors and cutoff values were identified as predictors of LBP in CEA: having a high body fat higher than 23% ( = 0.01) and trunk lateral flexor endurance lower to 65 s ( = 0.021), body fat being the strongest predictor.