This study examined the effects of question prompts, knowledge integration prompts, and problem solving prompts, embedded in a Web-based learning environment in scaffolding preservice teachers' conceptual understanding and problem solving in an ill-structured domain. A mixed-method study was employed to investigate the outcomes of students' conceptual knowledge and ill-structured problem solving. The quantitative results indicated that students who received knowledge integration prompts had significantly higher scores in overall problem solving performance, but the same was not true for prompts focused on conceptual knowledge. Further, the qualitative findings revealed the positive effects of knowledge integration prompts in facilitating students to make intentional efforts to identify and explain major concepts and their relationships that are necessary for solving the ill-structured problem. This study has implications for designing curricula in ill-defined domains that seek to integrate and promote the application of educational principles to real-world problems. (Contains 2 tables.)