<p>This study investigated the role of Generative Artificial Intelligence (GenAI) and metacognitive operations within the design process. A qualitative research approach was employed and Retrospective Think-Aloud protocols and semi-structured interviews were utilized to examine the design processes of five students under the Normal design condition (without GenAI use) and four students under the GenAI-assisted condition. The findings revealed that the use of GenAI was predominantly concentrated in the early phases of the design process, closely aligning with a divergent orientation. Under the GenAI-assisted condition, participants showed two key patterns: frequent phase transitions during the early phases and stabilization in the later phases, consistently concluding in the Design phase. Additionally, GenAI facilitated another pathway for iterations between the problem and solution spaces. Importantly, GenAI played a dual role in metacognition of design: it not only propelled design actions, but also created opportunities for reflection. In sum, GenAI functioned as a catalyst, enhancing both the quality and the occurrence of meaningful metacognitive operations.</p>