The media may not tell us what to think but it may tell us what to think about, this is the cardinal assumption on which the Agenda Setting Theory of the media revolved and it is on this that the research is anchored because one of the core ingredients of election is to mobilize many supporters because election is a game of majority and whoever has the majority carry the ballot. However, getting the majority requires lots of efforts and one of such efforts is to involve the mass media. It is on this notion that this research examined the role of Agenda Setting Theory in political communication in Nigeria elections with the view to know how the media played the agenda-setting role in the 2015 General Election in Lagos State and the kind of influence it has on the electorates. Survey research method was used and 200 copies of the questionnaire were administered to the respondents within Lagos state whereas 180 copies were returned. The data were analyzed using frequency and percentage table. Findings show that the sustainability of the democracy through public mobilization rest on the shoulder of the fourth estate of the realm (media) i.e what people know about the 2015 general election in terms of contestants, party manifestoes etc were as a result of what the media brought to their table. It is recommended that media should be free from a few influential politicians to avoid turning the media into tools of propaganda.