Percutaneous kyphoplasty (PKP) surgery is generally accepted as a minimally invasive treatment for osteoporotic vertebral compression fractures (OVCFs). However, hidden blood loss (HBL) caused by this procedure is usually disregarded. This study aimed to investigate the amount of HBL and its influencing factors after PKP surgery.A total of 160 patients were retrospectively examined from January 2014 to January 2016, and their clinical and radiological data were recorded and analyzed. Preoperative and postoperative hematocrit (Hct) and hemoglobin (Hb) levels were also documented. HBL was calculated using Gross formula. Different factors, including gender, age, bone mineral density (BMD), number of fracture levels, hypertension, diabetes mellitus, operative time, percentage of vertebral height loss, percentage of vertebral height restoration, and cement leakage, were examined. Multivariate linear regression analysis was performed to elucidate the related clinical or radiological factors of HBL.A total of 122 patients with 169 levels were eligible for inclusion in the study. The mean HBL was 279 ± 120 mL, and the postoperative Hb loss was 8.2 ± 3.9 g/L. Multivariate linear regression analysis revealed that HBL was positively associated with operative time (P = .000), percentage of vertebral height loss (P = .037), and percentage of vertebral height restoration (P = .000). By contrast, HBL was not associated with gender (P = .874), age (P = .148), BMD (P = .134), number of fracture levels (P = .079), hypertension (P = .259), diabetes mellitus (P = .495), and cement leakage (P = .975). The postoperative incidence of anemia significantly increased by 39.3% compared with that of the preoperative incidence (χ2 = 21.432, P = .000).For patients with OVCFs, the amount of HBL after PKP is much larger than that observed perioperatively. Operative time, percentage of vertebral height loss, and percentage of vertebral height restoration are influencing factors of HBL.