The internet is one of the most important communication technology media in human life. Internet marketing network creates a hope for business people to compete in marketing a product, not infrequently business people market their products with various promotions and are marketed through online media or using the internet network. Promotions that used to use old media, such as newspapers, radio and brochures, can now be replaced with a variety of the latest media that uses internet technology, such as social media, and websites. This research method uses a quantitative method with a descriptive approach and uses a path analysis test. The number of samples determined in this study was 100 people. This study concludes that promotion variables using Facebook and Instagram have a positive effect on consumer purchasing decisions at PT. EMKA Architect Group. In addition, the trust variable is also able to mediate the strong relationship between Facebook and Instagram promotion variables on consumer purchasing decisions at PT. EMKA Architect Group.