Alzheimer’s disease (AD) is a progressive neurodegenerative disease and the single commonest cause of dementia. Many other diseases can, however, cause dementia, and differential diagnosis can be challenging, especially in early disease stages. For most neurodegenerative dementias, accumulation of brain pathologies starts many years before clinical onset; the ability to detect these pathologies paves the way for targeted disease-modifying prevention trials. AD is associated with β-amyloid and tau pathologies, which can be quantified using cerebrospinal fluid and imaging biomarkers and, more recently, using highly sensitive blood tests. While for the most part, specific biomarkers of non-AD neurodegenerative dementias are lacking, non-specific biomarkers of neurodegeneration are available. This review summarizes recent advances in the neurodegenerative dementia blood biomarker research and discusses the next steps required for clinical implementation.