Nanomaterials have emerged as transformative tools in biomedical diagnostics, offering significant advancements in the accuracy, sensitivity, and versatility of diagnostic technologies. Their unique properties, such as high surface area, biocompatibility, and functionalization capabilities, enable enhanced detection of biomarkers and early disease diagnosis. This book chapter explores the role of nanomaterials in the development of diagnostic devices, focusing on their applications in biosensors, imaging technologies, and wearable health monitoring systems. Additionally, it examines their potential for personalized medicine and point-of-care diagnostics. Despite these promising advancements, challenges related to biocompatibility, scalability, regulatory concerns, and cost must be addressed. Looking forward, the integration of artificial intelligence with nanomaterials and innovations in miniaturization and flexibility of diagnostic devices offer exciting possibilities for smarter, more accessible healthcare. This review highlights the current state of nanomaterial-based diagnostics, future directions, and the barriers that must be overcome to realize their full potential in clinical practice.