<p>We present findings related to the enactment of an instructional sequence focused on hierarchical geometric relationships with elementary preservice teachers (PSTs). This is an important topic in elementary geometry that sets the stage for more rigorous study at higher grades. Previous research has noted challenges in teaching this topic in courses for PSTs. This study is informed by the commognitive theoretical framework. Whereas previous literature has framed the intended learning process in cognitive terms, we conceptualize PSTs’ learning process as a matter of discursive change. We document five important shifts in the participants’ geometric discourses, leading to the intended learning outcome. The main contribution of this work is a documented learning process regarding a challenging, underresearched topic. We demonstrate substantial progress, using a novel instructional approach informed by insights into PSTs’ discourses. Our findings can help mathematics teacher educators teach this topic effectively, thus better preparing PSTs to teach geometry.</p>