Non-attendance and delay for vaccination schedules remains a big challenge to healthcare workers. Among the frequently mentioned reasons for missed vaccination in children is forgetfulness of caretakers to show up in vaccination schedules. This necessitates developing an automated reminder system with integration of mobile technologies.This paper aimed to develop and test an automated mobile text message reminder system in the local context of Ethiopia.This system is developed using iterative development process through phases of requirement analysis, design, development, testing and refinement. Requirement gathering was done before development of the system. Front end application was developed using java technologies while back end applications were developed with oracle database. Finally, pilot testing of the automated reminder system was done on 30 participants.The automated system has been developed based on requirements. The text message reminder system has two components: 1. Web based application for client registration and automatic reminder scheduling; 2. SMS application for automatic SMS text messaging. In the pilot testing, all the text messages (100%) were dispatched from the automated system to the respective participants. Finally, the system has shown a notification that the text messages have been sent successfully.Text message reminder system has been developed for routine childhood immunization program in Ethiopian context. Text message based mHealth interventions should be carefully designed, developed, tested and refined before actual implementation.