Project-based learning may enhance students' cognitive skills and knowledge construction. Online discussion stimulates the social interactions of project-based learning, and appropriate cognitive tools (such as concept maps) facilitate the coordination, planning, and implementation of projects. Currently, related studies on project-based learning environments that integrate concept-mapping and discussion tools are sporadic. This study explored the behavioral patterns of learners' concept-mapping processes and the cognitive processing patterns of online discussion content conducted in a project-based learning environment equipped with both concept-mapping and online discussion tools. This study also compared the differences in behavioral patterns in the two main project-based learning phases: planning and implementation. This study employed content and sequential analyses to conduct empirical analyses with 48 college students as participants over a two-month period of teaching activities. The results showed that the behavioral patterns of learners exhibited more diversified operations and discussion during the planning phase. In addition, the use of concept mapping allowed participants to focus on the discussion task. This study proposes teaching practices and research recommendations based on the results.