With the continuing growth of urbanization and the boom of the construction sector in China, a substantial quantity of construction and demolition waste has been generated. However, there has been little research to characterize the waste from buildings’ interior renovation (repair and maintenance) or decoration activities. The primary purpose of this study was to provide a systematic analysis for the generation and flows of decoration and renovation waste based on field investigation. Taking Shenzhen city - a fast-growing megacity (over 20 M population) in South China - as an example, the results show that approximately 1 Mt of decoration and renovation waste was generated in Shenzhen city in 2017, with an annual growth rate of 10% over the past decade. Concrete waste and brick (block) account for 72% of the total decoration and renovation waste. The landfilling rate of decoration and renovation waste has reached 83%, of which a majority was disposed of by open dumping. The renovation of older residential buildings produced more than half of the total decoration and renovation waste. Although the amount of hazardous materials such as gypsum and painting materials only account for a very low weight fraction of 2%, they could still pose significant environmental impacts, compared to other types of construction and demolition waste. Accelerating the construction of sorting facilities to separate toxic and valuable materials is crucial, to realize decoration and renovation waste minimization and lower environmental risks. Overall, the findings of this study could be applied to formulate environmentally sound management measures from a policy standpoint, for Shenzhen city. The methods could also be useful for decoration and renovation waste estimation and projection in other cities in China and beyond. •This study characterizes the generation and flow of D&R waste in a megacity in China.•Approximately 1 Mt (50 kg per person per year) D&R waste were generated in 2017.•Landfilling rate reached to 83% and a majority were disposed of by open dumping.•D&R waste from residential building renovation is the major generator, by 27.5 kg/m2.•The cumulative generation of D&R waste could reach to 19 Mt from 2018 to 2030.