BACKGROUND: Neglected tropical diseases (NTDs) are diseases of poverty and affect 1·5 billion people globally. Conditional cash transfer (CCTs) programmes alleviate poverty in many countries, potentially contributing to improved NTD outcomes. This systematic review examines the relationship between CCTs and screening, incidence, or treatment outcomes of NTDs. METHODS: In this systematic review we searched MEDLINE, Embase, Lilacs, EconLit, Global Health, and grey literature websites on Sept 17, 2020, with no date or language restrictions. Controlled quantitative studies including randomised controlled trials (RCTs) and observational studies evaluating CCT interventions in low-income and middle-income countries were included. Any outcome measures related to WHO's 20 diseases classified as NTDs were included. Studies from high-income countries were excluded. Two authors (AA and TH) extracted data from published studies and appraised risk of biases using the Risk of Bias in Non-Randomised Studies of Interventions and Risk of Bias 2 tools. Results were analysed narratively. This study is registered with PROSPERO, CRD42020202480. FINDINGS: From the search, 5165 records were identified; of these, 11 studies were eligible for inclusion covering four CCTs in Brazil, the Philippines, Mexico, and Zambia. Most studies were either RCTs or quasi-experimental studies and ten were assessed to be of moderate quality. Seven studies reported improved NTD outcomes associated with CCTs, in particular, reduced incidence of leprosy and increased uptake of deworming treatments. There was some evidence of greater benefit of CCTS in lower socioeconomic groups but subgroup analysis was scarce. Methodological weaknesses include self-reported outcomes, missing data, improper randomisation, and differences between CCT and comparator populations in observational studies. The available evidence is currently limited, covering a small proportion of CCTs and NTDs. INTERPRETATION: CCTs can be associated with improved NTD outcomes, and could be driven by both improvements in living standards from cash benefits and direct health effects from conditionalities related to health-care use. This evidence adds to the knowledge of health-improving effects from CCTs in poor and vulnerable populations. FUNDING: None.