Background: Due to the high incidence of benign lesions in renal masses, numerous studies have been performed to clarify the value of core needle biopsies. The aim of the present study was to describe the complication rate after renal tumor biopsies (RTB), in order to make recommendations on observation after the procedure. Materials and methods: Data from all patients who underwent percutaneous ultrasound-guided RTB between February 2013 and October 2016 due to CT verified solid renal masses were prospectively collected and kept in a well-maintained database. Complications were collected retrospectively and classified according to the Clavien-Dindo (CD) classification system. Results: Data from 224 consecutive patients were retrieved. Thirteen patients underwent unilateral repeat biopsies and three patients underwent bilateral biopsies; thus, a total of 240 procedures were analyzed. A total of 124 patients (51.7%) were discharged within 4 hours after the RTB procedures and 110 patients (45.8%) were discharged within 24 hours. The remaining six patients (2.5%) were hospitalized for more than 1 day, all due to co-morbidities which were unrelated to the procedure. In total, five patients (2.1%) experienced post-biopsy complications: one case of iatrogenic pneumothorax, one case of spontaneously resolving hematuria and three cases of fever. All complications were CD ≤2 and all patients with complications were discharged within 24 hours, except for one patient who was hospitalized for 3 days due to management of bone pain. No correlation was found between the number of biopsies and complication rate. Conclusion: The overall complication rate following ultrasound-guided biopsies of renal tumors was low and all complications were mild. Given the current evidence, it is believed that ultrasound-guided RTB can be done as an outpatient procedure without the need for hospitalization.