The 2019 coronavirus disease (COVID-19) profoundly impacted the medical waste management system (MWMS). Nevertheless, there is a literature gap on dynamically examining how the disease outbreak affects this system. This article bridges the gap in theory and practice by presenting a novel system dynamics model for medical waste (MW) management. The proposed model includes disease outbreak and MW management sub-models for addressing the dynamic impacts of COVID-19 on waste generation and management patterns. In terms of theoretical contributions, the disease outbreak model consists of variables and interventions, including seasonal effects, hospital strain, public behaviour, personal protective equipment consumption, lockdown and vaccination. In addition, the MW management sub-model contributes to considering COVID-19 and non-COVID MW generation, waste management methods, carbon footprint generation and untreated MW accumulation. For implementing theoretical contributions in practice, the impacts of applying non-coercion social distancing, decreasing the death threshold, enhancing mask availability and coverage, earlier vaccination and lockdown implementation were assessed on the disease spread and consequently the MWMS. The case study of California provided managerial insights about how disease dynamics affect patterns of MW generation. Variation in waste generation patterns influenced the waste management methods, relevant environmental impacts and the risk of secondary infection by untreated MW. Finally, the impacts of MW treatment capacity expansion and district regulations on waste separation for increasing the share of recyclable materials were assessed on the amounts of accumulated untreated waste, the corresponding secondary infection risk, the amounts of landfilled waste and environmental impacts.