Background/Objectives: Percutaneous kidney biopsy (PKB) is a valuable diagnostic tool for evaluating renal masses and suspected renal cancer but carries a risk of hemorrhagic complications. This study aimed to determine whether injecting a hemostatic Gelfoam mixture into the biopsy tract reduces post-procedural bleeding while maintaining diagnostic accuracy. Methods: This retrospective study included 500 patients who underwent PKB at our hospital between 2019 and 2024. Patients were equally divided into two groups: Group A (n = 250) received Gelfoam injection into the biopsy tract, and Group B (n = 250) underwent standard PKB without Gelfoam. Hemorrhagic complications were categorized as mild, mild–moderate, moderate, or severe based on immediate and 4-h post-procedure CT findings. Management protocols included same-day discharge for mild cases (with next-day re-evaluation) and 24-h observation for mild–moderate cases. Results: Group A had significantly fewer moderate–severe hemorrhages compared to Group B (1.3% vs. 4.0%, p = 0.034) and a higher rate of same-day discharge (84% vs. 40%, p < 0.05). These differences led to a notable reduction in total hospitalization days (43 vs. 167) and decreased overall costs. Diagnostic yield was similarly high in both groups (98.5% vs. 97.8%, p = 0.72). Conclusions: Gelfoam injection during PKB effectively reduces hemorrhagic complications and shortens hospital stay without compromising diagnostic accuracy. Routine use of Gelfoam—especially in high-risk patients—is supported by these findings, and further prospective studies are recommended to validate these results.