Although there are many studies on the constructionist use of educational robotics, they have certain limitations. Some of them refer to robotics education, rather than educational robotics. Others follow a constructionist approach, but give emphasis only to design skills, creativity and collaboration. Some studies use robotics as an educational tool in engineering education, science and programming learning implying mindtools, but they do not give evidence of mindtool characteristics. This work proposes educational robotics as mindtools based on constructivism and especially constructionism. The positive learning results from two case studies on physics and programming teaching indicate that educational robotics can be used as mindtools supporting knowledge construction through the design of meaningful authentic projects, learning by doing in both the virtual and real world, facing cognitive conflicts and learning by reflection and collaboration.