The implementation of e-participation in Indonesia nowadays increases along with the rise of e-government. But, participation level in Indonesia is still lack behind other countries. Thus, it is needed to analyze factors influencing citizen's intention to participate electronically. This study examines factors influencing citizen to participate in e-participation service with Social Cognitive Theory (SCT) and Technology Readiness theory. The case study used in this study is LAPOR!, an online public aspiration system in Indonesia. Furthermore, this study is written to validate the use of SCT and extend it with technology readiness theory as technology adoption rate in developing country is not spread evenly. Research data is collected from 410 respondents and analyzed with Partial Least Square - Structural Equation Modelling (PLS-SEM). The empirical outcomes indicate two cognitive factors of SCT (participation self efficacy and outcome expectation personal) have significant impact towards intention to participate. Meanwhile, citizen's technology readiness implies their cognitive, in which influencing their intention to participate. Moreover, the result of this study helps government to improve and maximize e-participation potential so that government transparency can be achieved.