The purpose of this study was to investigate the association between pre-operative anemia and prolonged hospital stay among geriatric patients with operative femoral neck fractures. This retrospective cohort study was performed at a level I trauma center and included geriatric patients with femoral neck fractures (OTA/AO 31) and operative treatment with Current Procedural Terminology code 27236. Exclusion criteria were admission to the intensive care unit, evacuation of subdural hematoma, and conditions requiring exploratory laparotomy. A total of 207 individuals, with data collected between January 2015 and August 2019 and age 65 years and older, were included in the analysis. Linear regression was used to evaluate the association between anemia and length of stay adjusting for potential confounders. Anemia was defined using preoperative hematocrit. The primary outcome was prolonged length of stay, defined as 5 or more days. The group was 65% women. The mean age was 80.2 years (range, 64-98 years). The majority (61%) of patients had anemia. American Society of Anesthesiologists classification was associated with preoperative anemia (P=.02). Patients with anemia had a 16% higher risk of prolonged length of stay compared with patients without anemia (81% vs 65%, P=.009). In the linear regression model, preoperative hematocrit was associated with length of stay (P=.032) when adjusted for sex, age, preoperative tranexamic acid, preoperative hemoglobin, postoperative hemoglobin, and postoperative hematocrit. Length of stay was approximately 1 week in this study, with anemia being a statistically significant risk factor for prolonged length of stay. Health care providers and administrators can consider anemia on admission when predicting length of stay. [Orthopedics. 2023;46(4):211-217.].