Abstract: The development of the Standard Gauge Railway has proven to be one of the most important modes of transportation for both freight and passenger services. While this new development provides a positive transformation to formerly undeveloped areas, there have been cases where such developments have had an adverse effect on the environment and the people who reside there. The purpose of this research was to investigate the environmental effects of the Standard Gauge Railway (SGR) construction project on community Livelihoods in Ngong, Kenya's Kajiado County in Kenya. The households in Ngong's four villages, namely Kerarapon, Olepolos, Kibiko, and Kimika were the study's target population. The study employed mixed method approach and descriptive survey research designs. The target population was 510 household members in total. This study used Krejcie & Morgan's (1970) formula to get the sample size. The study sample size was 219, comprising of 211 household members and community leaders, 2 from each village. Both probability and non-probability sampling methods were used in the investigation. The researcher employed a stratified and simple random sample for the 211 household members in their probability sampling. The household head was targeted for quantitative data. For non-probability sampling, purposive sampling was employed to select the 8 community leaders 2 from each community. Data were collected through interviews and a questionnaire for household members. Both quantitative and qualitative data from the acquired data were statistically and thematically analysed. On the one side, concerns regarding the project's environmental effects included pollution, land degradation, and negative effects on the water supplies in a number of settlements, including Olepolos, Kibiko, and Kerarapon. However, the SGR building project enhanced Kimuka village's ecology. As such, the general conclusion of the study shows that the SGR project has to a greater extent, negatively affected the community livelihoods of the villages in Ngong, Kajiado North Sub-County in Kenya. 

Key words: Standard Gauge Railway Project, Construction, environment, community livelihoods, sustainable development