Sustainability concerns continue to rise for Indonesians, as they are the second-largest country, after China, responsible for the million metric tons of plastic waste in the ocean, which are mostly single-use plastic packaging, making non recyclable packaging one of the biggest threats to their environment. Millennials, as the current largest age population in Indonesia, are shown to be the most ecologically aware of these issues. However, it is still unclear whether Indonesian millennials have actively made decisions to switch their purchases to sustainably packaged products, as prior research in Indonesia has yet to focus on this. Hence the research's objective is to determine the factors of sustainable packaging that affects green purchase decision (GPD) in Indonesian consumers. Data was collected using a self-administered online survey; there were 150 usable responses that were analyzed using PLS SEM method. The findings of this research reported a significant and positive impact between green attitude, perceived environmental responsibility, green product experience, and environmental friendliness of companies to GPI, as well as GPI to GPD. These findings offer implications for marketing managers and product developers to further understand green consumers and develop strategies in relation towards green product packaging.