The aim of this study was to investigate factors influencing consumer buying decision towards selected fast moving consumer goods (FMCG) in Nairobi. Quantitative approach along with explanatory research design was applied. The study was conducted on consumer of laundry detergent in Nairobi. A sample of 385 respondents was taken through convenience no probability sampling method, of which a total of 288 valid responses were obtained and used for the analysis. Structured self-administered questionnaire was used to collect the primary data and using SPSS 20.0, both descriptive and inferential analyses were conducted for correlation and multiple linear regression analysis to attain the intended objectives. The Finding indicates that product quality, price, availability, advertisement and brand awareness significantly influence buying decision of consumers in Nairobi, but, product quality, price and availability were the most significant and the demographic profile of shoppers indicates that the market is highly dominated by the purchasing decisions of females within the households in Nairobi plus Retailer's recommendation, friend and family as well as exposure to brands in shops have been identified as the most important sources of information. An important implication for marketers is the development of marketing strategies based on the right knowledge of the decision maker and shopper. Results also give direction for companies and marketers of such products to give attention to consumer’s behavior to be successful.