This study, based on what are the international recommendations for the introduction of the History of Mathematics (HM) in the teaching of this discipline, seeks to describe the Portuguese reality. Thus, the study aims to know: (i) teachers’ training in HM; and (ii) their conceptions and practices about the use of HM in the classroom. An online questionnaire was answered by a group of 432 Portuguese Mathematics teachers of secondary education (7th-12th grades). Approximately half of the teachers
considered their training in HM obtained in their higher education as frequent or solid. Almost all categorized as non-existent or reduced their continuous education in HM. Regarding the teachers’ practices, an overwhelming majority reports using HM as a didactic resource in Mathematics class and only about a third do it rarely. Teachers resorted more frequently to textbooks and problems with a historical context and favored the use of HM in the introduction to mathematical content. As for the potential of using HM in teaching, teachers evaluated the didactic potential of HM very positively. The biggest constraints were related to the extension of the official curricula, the difficulty of evaluation and the scarcity of support materials.