Mobile applications are now being used for 21st-century learning, including alphabet learning. There are numerous mobile application products for online learning, particularly those relating to the alphabet ABC. It was revealed that previous mobile applications did not provide interactive activities that suited preschool students. Therefore, this study aims to develop Hooray! Hooray! ABC for learning the alphabet. This study employed Design and Development Research (DDR) as the research design, which is divided into three phases: Phase I - the needs of the application; Phase II - the design and development; and Phase III - the evaluation. ADDIE model is used as the instructional design to design and develop the mobile application. Two experts were chosen to validate the application. It was tested for usability and student performance on 35 preschool students. The results reveal that Hooray! Hooray! ABC can be used for learning the alphabet based on experts' agreement in terms of usefulness (96%), ease of use (97%), ease of learning (94%), and satisfaction (100%). In addition, the result shows that Hooray! Hooray! ABC can increase students' performance (t = 13.271, p = 0.00) in learning the alphabet, making it beneficial for preschool students, teachers, and schools. This study also acknowledged the limitations and future suggestions of this study.