This study aims to determine online purchase intention of green products among one of E-Commerce consumer in Indonesia using Extended Planned Behavior theory. Questionnaire was distributed and obtained 402 respondents who met the criteria as consumer of one of the E-Commerce in Indonesia aged 18 years and over, had and or will buy green products in the E-Commerce. The results showed that environmental concern, environmental knowledge, consumer attitudes, subjective norms and perceived behavioral control are directly positively and significantly related to online purchase intentions of green products. Positive and significant results were also showed by the indirect effect of environmental concern and environmental knowledge on online purchase intentions of green products, through consumer attitudes, subjective norms and behavioral control of perception as mediator variables.