Mobile-based micro-learning has gained a lot of attention lately, especially for work-based and corporate training. It combines features of mobile learning and micro-learning to deliver small learning units and short-term learning activities. The current study uses the lens of the Self-Determination Theory of motivation and proposes a series of Mobile-Based micro-Learning and Assessment (MBmLA) homework activities to improve high school students' motivation and learning performance in science. An experiment was conducted to evaluate the effectiveness of the proposed approach. One hundred and eight students of a senior-level high school in Europe were randomly assigned into either a control condition (conventional paper-based homework approach) or an experimental (MBmLA approach) condition. The study carried out for a period of 5 weeks. From the experimental results, it was found that, in comparison to the conventional paper-based approach, the proposed MBmLA approach enhanced students' basic psychological needs of self-perceived autonomy, competence, and relatedness and improved students' exam performance in terms of factual knowledge. Moreover, students self-reported greater learning satisfaction with the mobile-based microassessment and micro-learning homework tasks. Implications on educational practices as well as future research are discussed.