This article reports a feasibility study for the construction of a large green roof on a future multi-storey car park building in Singapore. In-depth technical analyzes were carried out on each layer of the green roof, analyzes of benefits for society, the environment and the economy, and financial analyses. Research on the contracting company to build this car park in Singapore is also identified along with the local incentive programs that support this green facility. Throughout all the analyses, a conclusion has been drawn based on the cost-benefit analysis which concludes that a large green roof on a parking building will be a good investment. The term “green roof” is defined as a rooftop garden that offers both environmental and economic benefits. benefits for the building. The green roof consists of soil and vegetation planted on a waterproof membrane. There are two different types of green roof: extensive green roof and intensive green roof. An extensive green roof system has an overall depth of 3 to 5 inches and is used as a living machine with limited public access except for maintenance purposes (green roof technology). The weight of an extensive green roof is between 60 and 150 kg per square meter (International Green Roof Association, 2014). On the other hand, an intensive green roof system has an overall depth of between 7 and 24 inches and is more suitable for use as a consumer garden or park (Green Roof Technology). The weight of an intensive green roof is between approximately 180 kg and 500 kg per square meter (International Green Roof Association, 2014). The UNLV car park, approximately 1,600 square meters per level, will be built opposite the National Library Board located in Bugis, Singapore. Due to the country… mid-paper… 180 for the monthly seasonal parking fee, the car park will earn an estimated S$933,120 per year. Highest Investment Return Ratio per annum= [(Earnings – Initial Investment)/Initial Investment]= [(S$933,120 - S$156,000)/S$156,000]= 4.98 Lowest Investment Return Ratio per annum = [(Earnings – Initial Investment)/Initial Investment]= [(S$933,120 – S$216,000)/S$216,000]= 3.32 The calculated investment return ranges from 3.32 to 4.98, which is considered quite ideal for UNLV parking application. Although the initial cost in building extensive green roof is much higher than building a bare roof, the long-term social, environmental and economic benefits are greatly observed. Using cost-benefit analysis, the magnitude of the benefits outweighs the increase in initial cost, so it is cost-effective to build a green roof on the UNLV parking lot.