An immense body of literature on astronomy studies has provided evidence that individuals perceive the lunar phases concept as difficult. Furthermore, many studies have shown erroneous explanations or alternative conceptions of lunar phases. However, there is also a need to understand how individuals construct an explanation of the Moon's phases. This paper aims to explore pre-service science teachers' construction process of their explanations regarding lunar phases through clinical interviews. The data were obtained from fourteen pre-service science teachers and analyzed, identifying their nodes and dynamic mental constructs. The results indicated that most pre-service science teachers did not organize their nodes in a manner consistent with normative scientific explanations. In addition, pre-service science teachers changed their dynamic mental constructs while explaining different lunar phases, utilizing different media such as drawing and three-dimensional models, and responding to prompted questions. It was suggested that different opportunities, including technology-enriched activities regarding phases of the Moon, should be provided for pre-service science teachers to reorganize their nodes.