Neurodegenerative diseases (NDDs), such as Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS), are characterized by progressive neuronal degeneration, leading to cognitive and motor dysfunction. Early detection is crucial for effective intervention, but clinical symptoms often appear after significant neuronal damage has occurred. Biomarkers—measurable indicators of biological processes—play a pivotal role in early diagnosis, prognosis, and therapeutic monitoring. This review explores the latest advancements in biomarker research, including cerebrospinal fluid (CSF) biomarkers, blood-based biomarkers, imaging biomarkers, and genetic markers. We discuss their clinical utility, challenges, and future directions in improving early detection and personalized treatment strategies for NDDs.