For more than three decades, citizen engagement in the political process in South Korea was strictly hampered by the harsh control of the public sphere by authoritarian regimes and mainstream media's failure to provide a democratic public forum. With the penetration of online and social media, the participatory culture of South Korea has significantly and qualitatively changed. During the last 10 some years, citizens actively used Internet media, such as online and social media, in mobilizing people for social and political causes. In recent elections, the use of Internet media has been considered one of the decisive factors of turnout and election results. The wide availability of information, the supply of unfettered discussion forums, and constant connectedness beyond space and geographical boundaries of the Internet are believed to work efficiently in leading citizens to the political process. However, unlike in Western countries, research to investigate the mechanism through which citizens engage in political affairs has been scant in South Korea. Drawing on the participatory democracy theory, this study examines how old and new media use in South Korea possibly change citizens' political attitudes and perceptions and how such changes subsequently trigger civic engagement in political affairs. Among various possible factors of political communication, this research pays special attention to the mediating roles of political efficacy and deliberation behaviors of the electorate during an election period in South Korea. A multitude of studies have proven that political efficacy is one of the most immediate attitudinal explanations of political action. As one acquires feelings of heightened political efficacy, one becomes more likely to get involved in the democratic process. Also, deliberation behaviors, such as political conversation and reflection on news played an important role in citizens' political life. This study explores how political efficacy and deliberation jointly affect the pathway that connects news consumption with political participation, drawing on prior political communication frameworks, such as the cognitive mediation model, the communication mediation model, and the O - S - R - O - R model. This study suggests a two-step mediation model which centers on the roles of deliberation and political efficacy in political communication. Particularly, the hypothesized model incorporates the interpersonal discussion component of the communication mediation model and the political efficacy component of the cognitive mediation model into one, in order to theorize a holistic information processing framework that channels the influences of news consumption on political engagement. The current study provides empirical evidence to the hypothesized model by carrying out two cross-sectional analyses and one auto-regressive analysis from the data of a two-wave panel survey that was conducted during the 2012 presidential campaign in South Korea. Findings reveal that political efficacy mediated the relationship between news attention and political participation. Political efficacy also played a mediating role between deliberation behaviors and political participation. In addition, deliberation behaviors mediated the relationship between news attention and political efficacy. Most important, the deliberation behavior and political efficacy jointly mediated the impact of news attention on political participation, supporting the hypothesized model of this study. Such results imply that interpersonal political discussion and intrapersonal reflection on political issues help citizens make sense of the information obtained from the media, and at the same time, boost the level of competence of their political beliefs. The results also suggest that deliberation and political efficacy play a pivotal role in connecting citizen's information seeking behaviors with political participation. The findings also show that, among diverse news channels, social media have the biggest performance power in explaining citizen engagement in the political process. In addition, the results of path comparisons demonstrate that the paths from news attention via online and social media to deliberation, political efficacy, and political participation were stronger in the Wave 2 model than in the Wave 1 model. The findings imply that online and social media are providing South Koreans a more effective pathway toward democratic participation than traditional media by motivating their deliberative and by shaping political attitudes. The present study makes a significant contribution to the understanding of the ways in which South Korean citizens take advantage of recent new media technologies to engage in political affairs. Considering that many South Koreans have long been excluded from the actual political process, this study's findings provide practical meanings in understanding how we can boost citizen engagement in the democratic process in this digital age. Additionally, the hypothesized model of the present research helps organize a large body of theories on news consumption and political participation in political communication. It also suggests larger social and cultural implications for a healthy democracy across countries beyond South Korea.