The present article investigates the potentialities of photo-elicitation as a technique in teacher professional development. This study analyses the process of eliciting dilemmas in four primary teachers, whose solution has proved to contribute to the teachers' education. To this end, the effect of different types of external observers' intervention in dilemma generation, participating in sessions developed with a specific photo-elicitation procedure, is explored. The knowledge pursued in order to meet the study objectives concerned inconsistencies between goals and practices and teachers' dilemmas. These inconsistencies and dilemmas are tacit and with multiple possible interpretations, and are therefore not measurable. They consequently require an interpretative research approach using a qualitative method of inquiry based on collective case studies. The results show that the inconsistencies introduced to the teachers, by questioning their teaching practice, are enough but not necessary to pose professional dilemmas. Solving these dilemmas led the teachers to change their conceptual and processual beliefs, as well as their teaching activities.