Given sparse literature examining receipt of behavioral health service in children and caregivers following traumatic brain injury (TBI), we sought to identify predictors of unmet need. We performed an individual participant data meta-analysis using generalized linear mixed-effect models to examine predictors of behavioral health service use and unmet need. We included 572 children, ages 3 to 18, who were hospitalized overnight following complicated mild to severe TBI between 2002 and 2015. Caregivers completed ratings of depression and distress, child behavior problems, family functioning, and behavioral health service utilization. For children, unmet behavioral health service need was defined as an elevation on one or more child behavior problem scales without receipt of behavioral health services. For caregivers, unmet need was defined as an elevation on either a depression or distress scale without behavioral health service utilization. Among those with behavioral health needs, rates of unmet need were high for both children (77.8%) and caregivers (71.4%). Poorer family functioning was related to more unmet need in children (F(1, 497) = 6.57, p = 0.01; OR = 1.8) and caregivers (F(1, 492) = 17.54, p < 0.001; OR = 2.7). Children with unmarried caregivers also had more unmet behavioral health service need than those with married caregivers (F(1, 497) = 12.14, p < 0.001; OR = 2.2). In conclusion, unmet needs are common after pediatric TBI and relate to family factors. The findings underscore the importance of monitoring service needs following pediatric TBI and point to disparities in service use.