Open-burning of municipal solid waste (MSW) is very common in Nigeria. Hence, this work estimated the emissions (greenhouse gases and others) from open-burning of uncollected MSW in Nigeria. The parameters (secondary data) used for the estimations were obtained from pertinent literature of MSW generation rate in Nigeria, level of uncollected MSW subjected to burning in Nigeria, oxidation/burning efficiency and others, 80.6% of wastes generated in Nigeria are combustibles. The National Bureau of Statistics showed that 52% of Nigerians lives in urban areas in the year 2020. With an annual mean growth rate of 2.62% between 2006–2020 (World Bank data), the urban population of Nigeria was estimated at 104, 885, 855 in 2020. The estimation for the year 2020 shows that the MSW generated by the urban population of Nigeria ranges from 16.8–25.3 million tons. With burning/oxidation efficiency ( $\eta$) of 0.58, between 2.4–3.7 million tons of the uncollected wastes are open-burned. This represents 14.7% of the total MSW generated in Nigeria for the year. IPCC guidelines show that only fossil-carbon wastes are climate-relevant for CO₂ emissions. Our estimation shows that 14.3% of the MSW generated in Nigeria contain fossil carbon. The total emissions for the three GHGs–carbon dioxide, methane and nitrogen oxides were between 798 to 1, 197 kilotons of CO₂-eq per year. Other emissions associated with open-burning of MSW was also estimated using their default emission factor. The findings suggest the urgent need for the country to transition to proper waste management system, which will include improved collection and disposal to sanitary landfills, to protect public health and the environment.