Little is known about the role of prompts to help learners solve ill-structured learning problems. Instructors do not devote adequate time to formulate pedagogically useful prompts, and the usefulness of different types of prompt is unclear. This mixed-methods study examined the role of argumentative prompts in the writing of essays based on business case studies. A significant (p < 0.001) relationship with a large effect size was found between the type of argumentative prompt (rhetorical and dialectical) and argumentative depth. Alternative argumentative positions were found to significantly (p < 0.001) mediate the relationship between argumentative prompt type argumentative depth with a large effect size. Verification and elaboration strategies were utilized in a similar way across both rhetorical and dialectical prompts. Dialectical prompts did not appear to be more effective than rhetorical prompts when using evidence strategies. Rebuttal appeared to be utilized more in response to dialectical prompts. The implications are that instructors should ensure that both rhetorical and dialectal prompts are provided in assignments involving ill-structured learning problems.