Introduction: Decompressive craniectomy (DC) is a last tier to control refractory intracranial pressure elevation in children with severe traumatic brain injury (sTBI), but the optimal timing is unknown. This study aimed to describe the association between timing of DC and in-hospital mortality in children with sTBI in Germany. Methods: A retrospective cohort study of the German national hospital discharge database (2016-2022) was conducted for cases < 18 years. Children undergoing DC following sTBI were extracted. Time from admission to DC were calculated as complete hours and data were compared between early (time to DC ≤ 2 hours) and late DC (> 2 hours). Hierarchical logistic regression models evaluated the association of DC timing with in-hospital mortality, functional outcomes (Pediatric Complex Chronic Conditions (PCCC) ≥2)), poor outcome (composite outcome of death or PCCC≥2), length of hospital stay, days on mechanical ventilation (MV) and coding of seizures. Results: Among 13,492,821 children hospitalized, 9,495 had sTBI. DC was performed in 598 cases with time to decompression ranging from 0 to 27 days. More than half of DCs (54.8%) were performed within the first two hours after admission. 164 (27.6%) deaths occurred, with a median time from admission to death of 2 days. Early DC had a higher case-fatality (37.4%) compared to late DC (15.8%), with higher odds of death (adjusted odds ratio [OR] 2.89; 95% confidence interval [95%CI] 1.43-5.85) and poor outcome (OR 1.22; 95% CI 0.71-2.21). However, in survivors, early DC was associated with a shorter duration of MV. No differences in functional outcomes were associated with the timing of DC. Conclusion: Children undergoing early DC exhibited a higher risk of case fatality and poor outcome, alongside with less days on MV in survivors.