The high consumption rate of YouTube media compared to other social media platforms is a notable feature of contemporary media usage. This is particularly significant in Indonesia, where the current situation demands increased political involvement, particularly among young people. Given the polarization among citizens, political expression through social media has emerged as an effective means of sharing opinions and views. YouTube, with its vast user base and accessibility, has become a prominent platform for such expression. Therefore, this study aims to evaluate the role of social identity, personal identity, source credibility, and word of mouth in political expression. Social Identity and Source Credibility Theories are integrated to form a study model. A sample of 435 YouTube users residing in Jakarta was obtained by distributing questionnaires through social media using the survey method. Furthermore, the Structural Equation Model (SEM) analysis showed that each social identity, personal identity, source credibility, and word of mouth directly affects political expression. The negative relationship between social identity and political expression, as well as source credibility with political expression, requires further study involving motivational and attitudinal variables.