<p> Background and objectives Preoperative anemia is a prevalent condition in pediatric surgical patients and is associated with adverse postoperative outcomes, including increased mortality and morbidity. However, its specific impact on postoperative mortality in pediatric craniotomy patients remains poorly understood. This study aims to investigate the association between preoperative anemia and postoperative mortality in children undergoing elective craniotomy. Method A retrospective cohort study was conducted using electronic health records of pediatric patients undergoing elective craniotomy at West China Hospital from January 2011 to May 2024. Preoperative hemoglobin levels were categorized based on WHO criteria for anemia severity. The primary outcome was 30-day postoperative mortality. Results A total of 2,456 pediatric patients were included. The overall 30-day postoperative mortality rate was 2.1%, and the incidence of composite morbidity was 25.6%. Preoperative anemia was significantly associated with increased 30-day postoperative mortality (adjusted OR 4.19, 95% CI 2.02–8.71 for mild anemia; adjusted OR 3.70, 95% CI 1.60–8.57 for moderate to severe anemia). Anemia also correlated with increased composite morbidity and transfusion requirements. Conclusion Preoperative anemia, even when mild, is significantly associated with increased 30-day postoperative mortality in pediatric craniotomy patients.</p>