This paper examines how large language models are transforming due diligence by increasing the speed, scale, and depth of investigative research while reinforcing the importance of human judgment. Drawing on practical experience building DiligenAI at Threat.Digital, it explains how AI improves scoping, monitoring, reporting, and enables new service offerings for firms. It also outlines the limitations and risks of LLMs, including hallucinations, misinterpretation, and credibility concerns, and highlights best practices for responsible use. The central conclusion is that AI enhances efficiency, but experienced investigators remain essential to delivering reliable and defensible results.