Electronic word of mouth (e-WOM) from E-commerce (EC-eWOM) and social media (SM-eWOM) became one of key faktor for consumer to search online information of a product and later to decide purchase decision. This research was conducted to analyze factors (EC-eWOM Volume, EC-eWOM Rate Extremism, ECeWOM Quality, EC-eWOM Source Credibility dan EC-eWOM Integrity) that suspected to became drivers for user to adopt eWOM on either E-Commerce or social media. Data was collected using questionnaire that distributed and filled by 170 respondents based on characteristics that already decided before. Validity, reliability and hypothetical testing for actual data that collected was analyzed using SEM-PLS analysis with software Smart PLS 3.2.3. Result of this study indicate that (1) ECeWOM Usefulness and EC-eWOM Credibility significantly influence EC-eWOM Adoption. (2) EC-eWOM Rate Extremism and EC-eWOM Quality significantly influence EC-eWOM Usefulness, but not with EC-eWOM Volume. (3) EC-eWOM Source Credibility and EC-eWOM Integrity significantly influence EC-eWOM Credibility. (4) EC-eWOM Credibility significantly influence SM-eWOM Adoption , but not with EC-eWOM Usefulness and EC-eWOM Adoption. (5) Mediating effect from EC-eWOM Adoption also not significantly influence SM-eWOM Adoption. / Electronic word of mouth (e-WOM) dari situs e-commerce (EC-eWOM) dan media sosial (SM-eWOM) menjadi salah satu acuan bagi konsumen dalam mencari informasi tentang produk secara online serta menentukan keputusan pembelian. Penelitian ini bertujuan untuk menganalisa faktor-faktor (EC-eWOM Volume, ECeWOM Rate Extremism, EC-eWOM Quality, EC-eWOM Source Credibility dan ECeWOM Integrity) yang diduga menjadi penentu seseorang dalam mengadopsi e-WOM pada e-Commerce maupun eWOM pada media sosial. Pengumpulan data dilakukan dengan menyebarkan kuisioner kepada 170 responden berdasarkan karakteristik responden yang telah ditentukan. Uji validitas, reliabilitas serta uji hipotesis dari data yang terkumpul dianalisa menggunakan SEMPLS dengan software Smart PLS 3.2.3. Hasil dari penelitian menunjukan bahwa (1) EC-eWOM Usefulness dan EC-eWOM Credibility mempengaruhi EC-eWOM Adoption secara signifikan. (2) EC-eWOM Rate Extremism dan EC-eWOM Quality mempengaruhi EC-eWOM Usefulness secara signifikan, namun tidak demikian dengan EC-eWOM Volume. (3) EC-eWOM Source Credibility dan EC-eWOM Integrity mempengaruhi EC-eWOM Credibility secara signifikan. (4) EC-eWOM Credibility mempengaruhi SM-eWOM Adoption secara signifikan, namun tidak demikian dengan EC-eWOM Usefulness dan EC-eWOM Adoption. (5) Pengaruh mediasi dari EC-eWOM Adoption terhadap SM-eWOM Adoption juga dinyatakan tidak signifikan.