This paper presents a residential access control system (RACs) using QR codes and the internet of things (IoT) to improve security and help house owners. The contribution of this paper is that it proposes two mechanisms in the authentication phase and the verification phase, respectively, to enhance residential access control. The main idea is using cryptography between smartphones and access control devices. The cryptography compares secret codes on the key server via the internet. The RACs can notify a user of the residential access status through the LINE application and show the statuses of devices through the network platform for the internet of everything (NETPIE) in real-time. We compare this system’s performance with that of the current access control methods in terms of security and access speed. The results show that this system has more security and has an access speed of 5.63 seconds. Moreover, this system is safer and more flexible than the comparative methods and suitable for contactless authentication.