Involving students in the co-design of educational curricula and practices can benefit both students and teachers. Students who participate in co-design may show better learning or increased agency or engagement. In the present study, we investigated what kind of science knowledge or practices can be learned by student co-designers while engaging in co-design practices and how that learning happens with six high school students. We created a model to guide the analysis of students’ learning with technology in co-designing processes. The results revealed that students learned engineering design process even if no explicit instruction on engineering learning was given. Also, our analysis suggested that co-designing with technology enabled learning of the engineering design process and potentially furthered learning of science because it promoted knowledge integration. The results have implications for understanding and enhancing engineering design and science learning through co-designing with technology.