The aim of the study is to design an effective instruction build on the Dick and Carey Model and game-based learning that enables an undiagnosed language learner of dyslexia, facing problems in vocabulary acquisition to acquire a pre-defined number of vocabularies in a given time. The method of the curriculum development study is based on a case study in a real-life context with quantitative and qualitative evidence that relies on multiple data collection tools such as checklist, interviews, questionnaire and report cards of the learner. The results of the study demonstrated that the capability of the dyslexic learner can be increased to acquire 55 vocabularies in a week, the same number expected from their peers. The performance increase of the learner can be attributed to a new method of learning English vocabulary through game-based learning supported with spaced repetition.