In several nations, caries in pre-school children remain a significant oral health issue. In an outbreak period such as the Coronavirus disease 2019 (COVID-19), remote contact and education aimed at the prevention of oral diseases and the preservation of children's oral health are more relevant than ever. Currently, the amount of published applications is far higher than the published scientific studies while the problems of usability remains vulnerable. The goal of this paper was to comprehensively document the phase of development and usability testing of a mobile application for diet and oral health, namely Gigiku Sihat, which was primarily intended to be used by parents and guardians of pre-school children. The mobile application was developed using the System Development Life Cycle principle. Apart from searching for the available oral health application on Android platform, the initial requirement gathering process consisted of situational analysis, concept generation, content development, and features and functional requirement determination. The mobile application design and implementation evolved at each phase before being finalised. Gigiku Sihat was successfully developed in the Bahasa Malaysia. Finalised Gigiku Sihat was installed on mobile devices to determine the usability using translated and validated System Usability Scale questionnaire namely Skala Kebolehgunaan Aplikasi Mudah Alih (SKAMA). The mean score usability with score of 68 and above was deemed to have good usability. This study found that Gigiku Sihat mean (SD) usability score was 77.0 (14.18). The results were promising as they showed that Gigiku Sihat had a good usability. Thus, the development of this mobile application focusing on diet and oral health served as a new source of oral health education and provided a necessary foundation in developing future improved mobile application development for parents in the prevention of early childhood caries.