Background In 2013, Japan established a standardized classification system for categorizing endoscopic sinus surgery (ESS) into types I–V, yet no evaluation has been conducted thereof. Objective We assessed the ESS trends and status in Japan, focusing on outpatient and inpatient surgeries. Material and Methods This descriptive retrospective cohort study used Japan’s National Database of Health Insurance Claims and Specific Health Checkups between 2014 and 2021. The distribution of ESS types I–V and outpatient and inpatient surgeries was analysed, along with age groups and regional differences, focusing on ESS type III. Results Overall, 427,813 ESS procedures were performed, with types III and IV being most common. Outpatient ESS type III increased substantially compared to inpatient surgeries. Younger individuals favoured outpatient ESS type III over inpatient surgeries, with substantial regional variations across prefectures. Conclusions and Significance The adoption of a standardized ESS classification in Japan has facilitated a detailed understanding of surgical trends. The shift toward outpatient surgeries, especially for type III ESS, aligns with global trends toward minimally invasive procedures and reflects changing patient preferences and healthcare delivery practices. Consequently, continuous monitoring and research are crucial for adapting surgical practices to the evolving healthcare needs and patient expectations.