Obtaining sufficient biocompatibility and targeting efficiency represent some of the greatest challenges for the development of diagnostic and therapeutic drugs aimed at ameliorating neurological diseases, especially neurodegenerative diseases and brain tumors. In this regard, the blood-brain barrier makes it particularly difficult to enable early diagnosis and treatment of these diseases. As a promising solution to these challenges, nanodiamonds (NDs) are an emerging class of carbon-based nanomaterials that display chemical inertness, good biocompatibility, prolonged photostability, negligible toxicity, and alternative surface functionalization. Owing to these unique physical and chemical properties, NDs have great potential for the diagnosis and treatment of neurological diseases. In this review, we explore the existing shortcomings and advantages of detection and treatment techniques for representative neurological diseases, with a focus on the use of NDs. We also discuss the potential mechanisms of NDs in the context of nano-enzymes and antiaging. Finally, we present an innovative strategy that eliminates aging cells via NDs for the potential diagnosis and treatment of neurological diseases.