question: WHAT IS ALREADY KNOWN ABOUT THIS TOPIC? Coronavirus disease 2019 (COVID-19) outbreaks in the past were mostly caused by overseas transmission, but if control measures are not appropriately applied, domestic transmission could also cause large-scale local epidemics. WHAT IS ADDED BY THIS REPORT? This report covers all information of epidemic investigation processes, epidemiological characteristics and exposure history, transmission chains, sequencing results as well as public health measures taken for the COVID-19 cluster epidemic caused by the Delta variant in a cosmetic hospital in Yantai City in August 2021. WHAT ARE THE IMPLICATIONS FOR PUBLIC HEALTH PRACTICE? The information provided in this report, including active case finding, community management, and mass testing, may assist public health professionals in dealing with local COVID-19 epidemics caused by domestic transmission.