During the last decade, Finnish teacher education (TE) has received special interest due to the Finnish students' success in PISA. Although TE in Finland has many strengths, there are also challenges that need to be addressed. One of the main challenges is the relation between theory and practice. As action research (AR) has been suggested as one possible tool for bridging the theory-practice gap and simultaneously supporting the forming of the foundational steps for an inquiry stance to continue through the teaching career, an AR orientation in the pre-service stages is of particular interest in this study. The aim is to explore student teachers' (STs') experiences of AR-based projects within two different contexts of Finnish TE, characterized by various paradigms: a class and a subject TE programme. The analysis revealed experiences of both constraints and affordances. Some of these are identified among both groups of STs, albeit somewhat differently characterized in the two contexts, while others are context specific. The results show that both groups of STs value their experiences of the AR-based projects. However, the results give important insights into STs' experiences of both constraints and affordances that merit further consideration when implementing AR-based projects within pre-service TE.