The fast rate of technological development in today's modern, digitalized society provides new opportunities and challenges for the future of geography education. The availability of geographic applications and geographical information systems (GIS) also create many interesting possibilities for the analysis, interpretation and production of geographic information (GI). The objective of this paper is to explore and discuss how a digital GIS portfolio can be used as an educational method for teaching and learning about the use of GIS. In this study, a design-based research (DBR) approach is used to develop a portfolio model for use in a Geomedia course in an upper secondary school setting. The design process occurred during January 2019 with pre-service teachers (n=8) and Geography teachers (n=2) at a university in Finland. There were six development cycles including problem analysis, design process and design solutions. The idea of a DBR approach is not only to create instructional materials to support students' in their learning and development of GIS skills, but also to be an educative process for pre-service teachers who have minimal experience in teaching GIS skills. The digital GIS portfolio model follows Bloom's taxonomy and includes progressively more demanding, inquiry-based activities for students. The digital GIS portfolio as a pedagogical practice was tested during Spring semester in 2019 with students (n=17) who were completing a Geomedia course at a local upper secondary school. It turned out that the use of a digital GIS portfolio is a very promising method for GIS education. Use of the portfolio improved student competence at using GIS; it developed student motivation to learn about GIS; and increased students' perceptions about the importance of GIS. However, a teacher-centered approach for teaching about GIS skills was also considered to be very important. The results of this study provide practical knowledge for Geography teachers and useful advice for developing teacher training in Geography.