Incorrect organic waste management can lead to several environmental and health threats. The literature shows that municipalities are adopting several strategies to reduce the improper disposal of organic waste. In 2019, Florianópolis, Brazil, became the first Brazilian state capital to approve a law on mandatory organic waste separation and composting, the Florianópolis composting law (FCL). Nevertheless, the successful implementation of this new regulation relies on acceptance among urban stakeholders and civil society. The role of social acceptance has not been investigated when dealing with new waste management regulations. To this end, 37 qualitative interviews with local stakeholders were conducted to determine the key factors influencing the acceptance of the FCL by analyzing stakeholders' perceptions of the relevant risks, benefits, hindering and promoting factors. The results show that the law could represent an important first step toward a sustainable municipal solid waste management system; however, several risks may arise in the absence of adequate monitoring systems. These risks are mainly linked to water contamination and health issues due to harmful insect proliferation. Furthermore, even though Florianópolis society seems culturally open, the lack of infrastructure and investments in the city could hinder the effectiveness of the law. Strategies for improving the law's effectiveness should be focused on supporting the existing formal and informal composting initiatives that have become widespread in recent decades. This could lead to a decentralized organic waste management system that empowers local initiatives and reduces the initial costs of implementing new composting systems and increases the separation rates at the household level. Display omitted •Stakeholders perceive benefits as well as risks related to the new policy (FCL).•Main perceived risks are: environment contamination and tax increase.•Main perceived benefits are: fertilizer provision and public costs reduction.•Supporting a decentralized waste management model can reduce initial FCL costs.•Well planned infrastructures and investments can support FCL effectiveness.