The study is geared towards finding out the role of mass media in electoral process and coverage of political parties activities in 2015 elections with reference to four media houses and four political parties i.e Osun State Broadcasting Corporation, Gold 95.5 F.M, Ilesa, Osun Defender Newspaper and Nigerian Tribune Newspaper. Political parties include: All Progressive Congress (APC), People’ Democratic Party (PDP), Labour Party (LP) and Accord Party (AP). It is revealed that the role and contribution of media in political awareness, mobilization, education and in the entire political development especially during election cannot be overemphasized. Quantitative research design was used in which cross-sectional survey method was adopted while the data collection instrument was questionnaire. 200 copies of questionnaires were administered and 180 were returned. Respondents were drawn using probability and non-probability technique. Also, the data were analysed and interpreted using table, frequency and percentage method. However, the sustainability of the democracy through public mobilization rest on the shoulder of the forth estate of the realm (media) which is achieved through media social responsibility and constitutional role. Similarly, most of the people in Osun state are affiliated to All Progress Congress and Peoples’ Democratic Party with majority of them participate in politics serving different roles as voters, party agents, pressmen, and election observers. It is recommended that journalist should try as much as they can to be fair in their news coverage so as to give equal coverage to all political parties.