Parafalcine and tentorial subdural hematomas (SDH) are infrequent but regularly occurring traumatic brain injuries (TBI). Appropriate management of patients with these injuries is unclear. The study objective is to derive and validate a clinical decision rule that identifies patients with parafalcine/tentorial SDHs that are at low risk for complications such that hospitalization may be avoided. This was a multicenter retrospective trauma registry and medical record review. Patients with parafalcine or tentorial SDHs had their data from the trauma registry collected and additional data was abstracted from the medical record using standard chart review methodology. The outcome considered was significant injury. This was defined as: any injury that underwent neurosurgery, death, or discharge to a rehabilitation/skilled nursing facility. The clinical decision rule was derived by identifying variables independently associated with the outcome of interest using multivariable logistic regression. The decision rule was then validated on a separate cohort of patients abstracted without knowledge of the decision rule. In the derivation sample, 136 patients with parafalcine/tentorial SDHs were identified. The mean age was 63 ± 19 years and 84 (62%) were male. Seventy-two (53%) had significant injuries. Variables independently associated with a significant injury included: age ≥ 60 years, adjusted odds ratio (aOR) = 3.71, (95% CI 1.37, 10.06), initial Glasgow Coma Scale score < 15, aOR = 8.30 (95% CI 3.14, 21.93) and additional TBIs on CT, aOR = 6.35 (95% CI 2.67, 15.13). In the derivation set, these three high risk variables had a sensitivity = 72/72 (100%, 95% CI 96, 100%) and specificity = 13/64 (20%, 95% CI 11, 32%). In the validation sample, the mean age was 62 ± 21 years and 48 (59%) were male. The three high risk variables had a sensitivity for significant injury of 26/26 (100%, 95% CI 89, 100%) and specificity = 7/55 (13%, 95% CI 5.3, 24%). All 35 patients who underwent neurosurgery had additional TBI findings on their cranial CT scan. Patients with parafalcine/tentorial SDHs who have initial GCS score < 15, are 60 years of age or older, and have other TBIs on their CT are at increased risk of complications and require hospitalization.