Geometric concepts are fundamental to early geometry education, and developmentally appropriate practices are crucial for teaching them to young children. Robotic coding is an effective tool in many areas of early mathematics and has significant potential in teaching geometric concepts. This study aimed to test the impact of a research-based robotic coding program on young children's understanding of geometric concepts. A quasi-experimental design was used with two intervention groups. The study involved 52 5-year-old children from a public kindergarten. The intervention-1 group (n = 18) received a research-based robotic coding program, while the intervention-2 group (n = 16) received a research-based no-coding program. The non-intervention group (n = 18) attended their regular program. Data on participants' understanding of geometrical concepts was collected through individual interviews using a geometric shapes classification test. Hierarchical linear modeling (HLM) was utilized to assess the effectiveness of two interventions. The results showed that both interventions had a significant effect with the robotic program being more effective. Additionally, follow-up tests indicated that both interventions had a lasting effect on the children's understanding of geometrical concepts. The study highlighted the potential of incorporating robotic coding and relevant research in fostering young children's geometrical development.