Parkinson’s disease (PD) is the second most common neurodegenerative disease. The accumulation of misfolded α-synuclein and progressive neuronal loss are its main characteristics. To date, no reliable values of cerebrospinal fluid (CSF) or serum markers have been established in routine clinical practice. Future biomarker research is needed to improve the accuracy of early diagnosis, clarify subtypes, and monitor disease progression. This book chapter provides an overview of the present (potential) blood and CSF biomarkers in human PD and mouse models. In particular, the recent detection of misfolded α-synuclein in CSF with α-synuclein seed amplification assays, which distinguishes PD patients from healthy controls with high sensitivity and specificity, represents a potential CSF biomarker for the early assessment and classification of PD patients.