Recently, the efficacy was demonstrated of the Diamondback 360® Coronary Orbital Atherectomy System (OAS) (Cardiovascular Systems, Inc., St. Paul, MN, USA) for treating calcified coronary lesions in percutaneous coronary intervention (PCI). The safety and feasibility of OAS application through a 5-Fr guiding catheter (GC) which is less invasive and reduces access site complications were validated. This sequential, retrospective, observational study was conducted in a single center from September 2018 to May 2020. The primary endpoint was a successful PCI with the OAS. Secondary endpoints were major adverse complications related to PCI with the OAS, including coronary dissection, perforation, side branch loss, need for an unexpected cardiac assist device, access site complications, and major adverse cardiac and cerebrovascular events. 33 PCIs in 30 patients (mean age 72 ± 11 years; male, 83.3%) were surveyed. All PCIs were successfully completed with OAS application through a 5-Fr GC. Coronary perforation after the OAS procedure occurred in one case (3.0%). Severe coronary dissection occurred in three cases (9.1%), and procedural myocardial infarction in two cases (6.1%). Regarding PCIs performed with the 5-Fr GC, the OAS is a safe and feasible strategy for calcified plaque modification.