Geometry strand receives limited attention in teaching of mathematics generally. One of the factors for this practice is that many mathematics teachers lack confidence in the teaching of geometry, as a result, they ignore teaching it. The problems students face in learning geometry emanate from how it is taught by most mathematics teachers. This paper investigated students’ alternative conceptions and misunderstandings regarding triangles in the Eastern Cape Province of South Africa and conducted an intervention using polygon pieces in teaching triangles. A diagnostic test was administered to assess 58 Grade 8 students’ levels of understanding of triangles with more emphasis on their properties, and a post-test was administered to evaluate the intervention. Descriptive analysis was employed for both tests. The qualitative analysis focused on aligning the students’ responses with the Van Hiele levels of geometric thinking. The findings indicated students’ alternative conceptions and lack of understanding of the properties of triangles. Also, the intervention enhanced the students’ performance from a 16% average in the diagnostic test to 82% performance in the post-test. We, therefore, recommend the use of polygon pieces to enhance students’ conceptual understanding of geometry.

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