Abstract: This paper investigated the influence of social media on voter behaviour during 2017 presidential elections in Kenya. The study was conducted in Kitisuru Ward of Westlands Constituency, Nairobi County, Kenya. This is as a sequel to the fact that many studies have been conducted globally including in Kenya on the use of social media during election campaigns. However, there is little evidence on studies undertaken on the influence of social media on voting behaviour of voters during the 2017 presidential elections in Kenya. The study was guided by three objectives: To identify social media platforms used by voters during 2017 general elections, to investigate on the uses of social media by voters during 2017 general elections and to determine whether social media usage influenced voters’ decision making during 2017 presidential elections in Kenya. The study adopted Two-step communication theory as theoretical underpinning for the research. A descriptive survey design was used. The target population of the study was registered voters in Kitisuru Ward. The target population therefore was 1198. Yamane [1967] sampling formula was used to get sample size of 400 respondents. The researcher obtained 248 questionnaires representing 62% response. Data was collected using research assistants. Data was presented using Frequencies, Percentages and Tables and was analysed using Statistical Package for Social Sciences [SPSS V.22]. Study findings revealed that 77% of respondents confirmed that social media influenced their decision making during 2017 presidential elections, while 23% said that they were not influenced by social media in choosing their preferred candidates during the same elections. The study also revealed that Twitter, Facebook, Whatsap, YouTube and Instagram were the main social media platforms used by voters in that order during 2017 elections. On perceptions, the study further revealed that 45% of respondents confirmed that they used social media to express their political ideology, 31.5% said social medial increased knowledge of parties contesting in the election while 23.5% said social was an effective platform through which they discussed politics. The study concluded that information on social media had great influence on voters as they decided on their preferred presidential candidate during 2017 elections. The study also concluded that, Twitter was the most popular social media platform followed by Facebook that was used by voters during 2017 election. Key Words: Social media, Voting behaviour, 2017 general elections, Twitter, Facebook