The sustainability challenges facing humankind make necessary the convergence of Science Education (SE) and Education for Sustainable Development (ESD). Science learning and ESD requires the adoption of student-centred transformative teaching methods that promote values and critical thinking. This article explores the role of citizen science (CS) as an educational tool that could contribute in such transformative teaching. Innovative ICT tools that enable teachers to more easily engage their pupils in CS-based activities tailored to their local environment and teaching objectives have been developed and implemented in eight case studies, involving 214 students and seven teachers from three schools in Greece, the United Kingdom, and Spain. The results showed that: a) the CS-based educational initiatives contributed to improving natural science learning and represented progress in the development and integration of students' competencies for sustainability; b) the developed ICT tools increased students' interest and motivation; c) versatile ICT tools and platforms for teachers' co-working can contribute to the inclusion of CS in the curriculum and thereby to the inclusion of ESD in schools. We conclude that such educational initiatives can contribute to the convergence of SE and ESD and help students develop global skills, preparing them for 21st century sustainability challenges.