With authentic English input and multimedia features, English storybook apps have the potential to be used as an effective learning tool for parent-child shared reading practice in families in English as a second or foreign language settings. This cost-effective educational technology may be particularly beneficial for those children from low socio-economic backgrounds in developing countries and language minority families in English speaking countries. However, most of the commercialized English storybook apps on the market are not designed to support parent-child joint engagement, especially for parents with limited English proficiency. Lack of theoretical and empirical evidence can be found to inform app designers and researchers on what design features should be included to facilitate dialogic reading and second language acquisition for this learner population. To this end, this dissertation fills in these research gaps by: 1) designing an interactive English-Chinese storybook app for young children and parents whose first language is Chinese to practice dialogic reading and learn English at home; 2) conducting an evaluation study to examine the learning effectiveness of the innovation and how it interacts with the child and parent characteristics; and 3) conducting a randomized controlled trial to examine whether and to what extent the embedded discussion prompts impact children’s learning and exploring how parents and children responded to these prompts. Using contextual inquiry and participatory design techniques, we identified demands and design challenges of English storybook apps for this learner population and developed an interactive multimedia storybook system with five design features which can effectively facilitate parent-child joint engagement and children’s learning. We found that embedding bilingual discussion prompts in the storybook app significantly promoted children's story comprehension and retelling. Our qualitative analysis of parent-child interactions revealed that the discussion prompts with feedback allow parents to practice dialogic reading strategies and provide scaffolding to their children naturally and effectively without explicit training. With parents translating and elaborating the story, children received more comprehensible input, thus enhancing their comprehension. The design of the questioning avatar further established children’s parasocial relationship with the story character and boosted their motivation. Together, this dissertation contributes to the fields of educational technology, language and literacy, human-computer-interaction by shedding light on the design, affordances, and educational effectiveness of interactive bilingual storybooks for children and their parents from linguistically diverse backgrounds.