Background: Total hip arthroplasty (THA) is a very successful surgery in restoring a patient's quality of life. Infection is a devastating complication of THA. Many risks factors for infection in THA have been identified but little is known of the effect by preoperative hematocrit. Purpose: We aimed to evaluate the effect of preoperative hematocrit on early superficial site infections, deep infections, and deep organ space infections. Methods: Our study cohort included patients undergoing a THA in the ACS National Surgical Quality Improvement Program database from 2006 to 2015. We conducted a multivariate logistic regression analysis to evaluate an association between preoperative hematocrit and infection controlling for patients demographics and known risk factors. Results: A total of 98,869 patients were identified in this study. Of these, 702 (0.71%) developed a superficial site infection, 314 (0.32%) a deep infection, and 226 (0.23%) an organ space infection. Our results suggested a significant increased risk of deep infection (OR = 2.38, p = 0.0120) and organ space infection (OR = 3.05, p = 0.0234) in patients with lower preoperative hematocrit (<41). In addition, patients with lower preoperative hematocrit had higher chance to receive postoperative transfusion (OR = 2.93, p < 0.0001). However, no significant associations between preoperative hematocrit and superficial site infections (p = 0.8554), wound dehiscence (p = 0.0660) and DVT (p = 0.9236) were detected. Conclusion: Low preoperative hematocrit is associated with increased risk of deep, organ space infections, and postoperative transfusion in THA, but not with superficial site infections, wound dehiscence and DVT.