ABSTRACT. The ease of usage of mobile phones led to its adoption by the users as personal digital assistant. This adoption, no doubt made it a lucrative target for cyber-criminals. A mobile phone can get into the hands of criminals through theft or loss. When this happens, the stored data can easily be compromised if the mobile phone is not protected with a password. To avoid this, developers of the mobile phone operating system included various screen lock options as the first line of defence to prevent unauthorized access to the mobile phone and by extension, the stored data. Various studies on the use of these screen lock options revealed that most end-users do not generally make use of it. To solve this problem, an Auto-reminder Persuasive System (APS) was developed. The system was implemented using Android SDK and JAVA. A pilot test was carried out using purposive selection of 1000 participants randomly divided into two equal groups of 500 members labeled A and B for experimental and control groups respectively. In the experimental group, APS was installed on the mobile phones of the members, while in the control group there was no installation of APS. At the end of the three months of the pilot test, the mobile phones of members of the two groups were collected and attempts were made to use the phones. The result from group A showed that 98.40% of members of the group passworded their phones as against the 24.00% from group B. With this result, it showed that APS is a highly promising method of persuading end-users to use password in protecting their mobile phones against unauthorized access.