The use of the student accommodation room security system at the Universiti Pertahanan Nasional Malaysia (UPNM) is now no longer considered efficient due to several problems experienced by the students themselves such as the limited provision of accommodation room keys causing difficulties due to the need to share keys, loss and damage to property in the accommodation room as a result of break-ins and waste of time and energy by students to follow procedures to replace new dorm room keys. Now with the Smart Key System can increase the level of security and make it easier for students to access their accommodation. The system equipped with Arduino Uno microcontroller hardware allows students to access using a password pin and also through an Android smartphone application. This system has a security feature in sending Short Messaging Services (SMS) notifications to registered user phone numbers. All user and administrator information for this system such as full name, username, application/web password and even phone number are stored in the MySQL database. In addition, the website for system administrators was developed using HTML, BOOTSTRAP, CSS and PHP while the Android application for users was developed using Kodular and PHP. Overall, the Smart Key system that was developed can improve the safety and convenience of students while also helping administrators to monitor the progress of the system.