This article aims to identify and understand the mathematics teachers’ geometric knowledge, when addressing geometry concepts for students at Middle School. For this purpose, the theoretical tool Knowledge Quartet (KQ) is used to identify and analyze the dimensions of knowledge that are revealed in the actions triggered by two teachers in the classroom. The research context took place in a process of continuing education in geomet r y, in a g roup with collaborative characteristics. The data were produced through audio and video recording and later transcribed. Critical events were selected of the investigated environment. In addition to being a theoretical tool that identifies the teacher’s mathematical and didactic knowledge in practice, according to the results, the KQ contributed to identify gaps associated with the teacher’s difficulties in face of the contingencies that present themselves in the context of geometry teaching.