Purpose of reviewCurrently, no disease modifying therapies (DMTs) have been approved for use in dementia with Lewy bodies (DLB). Clinical trials face difficulties due to the clinical and neuropathological heterogeneity of the condition with a diverse array of neuropathogenic mechanisms contributing to the clinical phenotype. The purpose of this review is to describe how recent advances in the development of biofluid biomarkers may be used in clinical trials to tackle some of these challenges.Recent findingsBiomarkers are essential both to support the accurate diagnosis of DLB and to delineate the influence of coexisting pathologies. Recent advances in the development of α-synuclein seeding amplification assays (SAA) allow accurate identification of α-synuclein from the prodromal stages in DLB. Additionally, validation of plasma phosphorylated tau assays in DLB is ongoing and offers an accessible biomarker to indicate the existence of AD co-pathology. Use of biomarkers for diagnosis and group stratification in clinical trials of DLB is growing and likely to be of increasing importance in the future.SummaryIn vivobiomarkers can enhance patient selection in clinical trials allowing greater diagnostic accuracy, a more homogeneous trial population, and stratification by co-pathology to create subgroups most likely to derive therapeutic benefit from DMTs.