This study presents a novel approach to support management scenarios using a large language model (LLM) based decision support system (DSS) that integrates a Rational Decision-Making (RDM) framework with ChatGPT to evaluate alternative courses for action. The automated evaluation considers the problem, company context, confounding factors, and outcomes’ ramifications. 72 business professionals tested the system’s feasibility using their own management decision cases, assessing DSS output across six parameters: understanding, multifaceted deliberation, output reliability, explainability, originality, and applicability. Results indicate ChatGPT’s feasibility for the DSS task, with scores generally at or above 4 out of 5 across most parameters and domains. No significant differences were found across gender, business domains, or investment scenario types, suggesting consistent system performance. However, older and more experienced professionals assessed originality and applicability significantly more critically (Cohen’s d = 0.45–0.61), indicating that domain expertise raises expectations for creative and practically grounded recommendations.