The goal of this research was to assess the influence of social media advertising on the buying decision-making process of consumers, using the case of leading online shopping sites in Kenya. the theory of reasoned action was used to frame this investigation. The study was conducted using a descriptive research approach, and the participants were management staff from five online shopping sites situated in Nairobi, Kenya. The population of study included members of staff in the management of top five (5) selected Online Shopping Sites in Kenya: Jumia, Kilimall, Jiji Kenya, Masoko and Copia. After randomly selecting 200 respondents from the target population, the stratified sampling approach was used to pick an unbiased sample of 133 respondents from the target population of 200 respondents. Primary data was gathered via the use of questionnaires. The research issued a total of 133 questionnaires and a total of 90 were filled and returned giving a response rate of 68%. The data will be analyzed with the help of the Statistical Package for Social Sciences (SPSS) software. For ease of understanding, data was coded according to various variables and descriptive statistics such as frequencies, means, and standard deviations. Analysis of regression and correlation were carried out in order to analyze and establish the link between the variables under investigation. The findings on the effect of use of social media advertising on consumer buying decision revealed that respondents agreed that the social media pages is interactive and it influences consumers shopping experience, Facebook and Twitter pages offer content aligned with the brand and gives consumers reasons to keep engaging with the company, making emotional connections through positive consumer experiences, exceptional service and engaging conversations has significantly influenced social media marketing. Respondents also agreed that changing the conversation and engaging fully with existing consumers increases the level of social media marketing. The study recommended that Online shopping sites should develop an online platform that will be engaging fully with existing consumers, providing sufficient information and personal, interesting, timely and responsive.