Tokopedia is an online shopping site based on C2C e-marketplace in Indonesia. The purpose of this research is to see the role of interactivity, trust and perceived effectiveness of e-commerce institutional mechanism (PEEIM) towards repurchase intention in Tokopedia e-marketplace, particularly in the JABODETABEK regions. Using online questionnaire, the study was conducted with 363 respondents residing in the JABODETABEK areas. They had transacted on Tokopedia, with the minimum age of respondents being 18 years old. The variables used in this study were measured using the Likert scale. Data were collected using the non-probability sampling technique combined with the convenience sampling method. This study used Structural Equation Modeling (SEM) WarpPL S 5.0 program for data processing. The results of this study confirm the positive relationship between trust in seller and customer satisfaction that further contributes to repurchase intention at Tokopedia online site. Other results also support the positive effect of using message boxes and feedback systems on variable interactivity but the message boxes did not help increase confidence in the seller. On the other hand, the PEEIM variable moderates negatively the relationship with trust in seller, interactivity, repurchase intention and customer satisfaction. / Tokopedia merupakan situs belanja online yang berbasis C2C emarketplace di Indonesia. Tujuan dari penelitian ini adalah untuk melihat peranan pengaruh variabel interactivity, trust dan perceived effectiveness of e-commerce institutional mechanism (PEEIM) terhadap repurchase intention di e-marketplace Tokopedia di wilayah JABODETABEK pada khususnya. Metode penelitian dilakukan kepada 363 responden yang pernah bertransaksi di Tokopedia yang berada di wilayah JABODETABEK dengan umur minimal responden 18 tahun keatas. Variabel-variabel yang digunakan dalam penelitian ini diukur dengan menggunakan skala likert. Teknik pengumpulan data menggunakan teknik nonprobability sampling dengan metode convenience sampling. Untuk pengolahan data dalam penelitian ini menggunakan Structural Equation Modelling (SEM) dengan menggunakan program WarpPLS 5.0. Hasil penelitian ini menegaskan hubungan positif antara trust in seller dan, customer satisfaction yang selanjutnya memberikan kontribusi terhadap repurchase intention di situs online Tokopedia. Hasil lainnya juga mendukung pengaruh positif penggunaan message box dan feedback system pada variabel interactivity namun tidak membantu meningkatkan kepercayaan pada penjual. Sedangkan variabel PEEIM memoderasi secara negatif hubungan dengan trust in seller, interactivity, repurchase intention dan customer satisfaction.