In recent trends, smart buildings have become the base for the Internet of Things (IoT). The usage of the internet is increased by connecting the devices in the homes to make the places more comfortable, provident, delightful, and secure. The proposed approach addresses a security aspect in smart home technologies, namely the door lock system. The door lock system determines the security by allowing the owner to monitor the buildings with a Smartphone-controlled, Bluetooth-connected system using Arduino UNO. Users can open or close the door lock by installing the developed android application in devices like tablets, smartphones, laptops, etc. by providing the login credentials like username and password which is verified in the database over the internet. If the credentials are invalid, the buzzer rings and an SMS alert is sent to the owner of the building which enhances the security. This approach can further be scaled to commercial sectors like ATMs, vending machines, etc. by using other wireless communication.