Liquid biopsy, a minimally invasive diagnostic method, offers early detection and monitoring of diseases by analyzing biomarkers in biofluids. However, its practical implementation faces challenges due to the rarity and complexity of biomarkers like circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and exosomes. Optical nanomaterial-based biosensors provide enhanced sensitivity and stability, making them promising for liquid biopsy. This review summarizes recent advancements in optical nanomaterials for detecting various biomarkers, including proteins, peptides, ctDNA, miRNAs, exosomes, and CTCs. These nanomaterials, such as metallic nanoparticles, quantum dots, and carbon nanomaterials, offer unique optical properties for sensitive detection. The review highlights the use of optical nanomaterials in improving detection performance, enabling ultrasensitive and accurate quantification. Despite challenges like low biomarker abundance and short half-life, optical nanomaterials show potential for overcoming these limitations. The review also discusses the importance of multiplexed detection and the role of optical nanomaterials in enhancing the feasibility of liquid biopsy. Overall, optical nanomaterials are crucial for advancing liquid biopsy techniques and providing insights into disease mechanisms.Liquid biopsy, a minimally invasive diagnostic method, offers early detection and monitoring of diseases by analyzing biomarkers in biofluids. However, its practical implementation faces challenges due to the rarity and complexity of biomarkers like circulating tumor cells (CTCs), circulating tumor DNA (ctDNA), and exosomes. Optical nanomaterial-based biosensors provide enhanced sensitivity and stability, making them promising for liquid biopsy. This review summarizes recent advancements in optical nanomaterials for detecting various biomarkers, including proteins, peptides, ctDNA, miRNAs, exosomes, and CTCs. These nanomaterials, such as metallic nanoparticles, quantum dots, and carbon nanomaterials, offer unique optical properties for sensitive detection. The review highlights the use of optical nanomaterials in improving detection performance, enabling ultrasensitive and accurate quantification. Despite challenges like low biomarker abundance and short half-life, optical nanomaterials show potential for overcoming these limitations. The review also discusses the importance of multiplexed detection and the role of optical nanomaterials in enhancing the feasibility of liquid biopsy. Overall, optical nanomaterials are crucial for advancing liquid biopsy techniques and providing insights into disease mechanisms.