Background Imaging-guided percutaneous biopsy of renal masses is regarded as safe and is widely used for histopathology diagnosis before treatment. Recommended observation time after tumour biopsy varies in international guidelines and the literature is sparse. Purpose To assess the effect of a 1-h post-biopsy observation time of percutaneous image-guided renal mass biopsy. Material and Methods This was a single-centre retrospective study. During January 2015 to September 2019, a total of 484 patients underwent renal mass biopsies. 4-h-observation-group: 178 patients and 1-h-observation-group 306 patients. All records were retrospectively reviewed, and data such as complications was obtained and compared between the two groups. Results A total complication rate of 4.5% ( n = 22) without any major complications (Cardiovascular and Interventional Radiological Society of Europe-grade (CIRSE) 5–6). Furthermore, a non-significant difference of 1.3% of the 1-h group and 3.4% in the 4-h group experiencing complications was found ( p = .18). A total biopsy-accuracy of 84% was observed. Conclusion This study shows that renal mass biopsy is safe with no major complications. This suggests that an outpatient approach with 1-h-observation time can be safely implemented for renal mass biopsy.