IntroductionStarting cancer treatment early can improve outcomes. Psychosocial factors influencing patients’ medical help-seeking decisions may be particularly important in low and lower middle-income countries (LMIC) where cancer outcomes are poor. Comprehensive review evidence is needed to understand the psychosocial influences on medical help-seeking for cancer symptoms, attendance for diagnosis and starting cancer treatment.MethodsMixed-methods systematic review registered on PROSPERO (CRD42018099057). Peer-reviewed databases were searched until April 2020 for studies assessing patient-related barriers and facilitators to medical help-seeking for cancer symptoms, diagnosis and treatment in adults (18+ years) living in LMICs. Quality of included studies was assessed using the Critical Appraisal Skills Programme tool. Data were synthesised using meta-analytic techniques, meta-ethnography or narrative synthesis as appropriate.ResultsOf 3963 studies identified, 64 were included. In quantitative studies, use of traditional, complementary and alternative medicine (TCAM) was associated with 3.60 higher odds of prolonged medical help-seeking (95% CI 2.06 to 5.14). Qualitative studies suggested that use of TCAM was a key barrier to medical help-seeking in LMICs, and was influenced by causal beliefs, cultural norms and a preference to avoid biomedical treatment. Women face particular barriers, such as needing family permission for help-seeking, and higher stigma for cancer treatment. Additional psychosocial barriers included: shame and stigma associated with cancer such as fear of social rejection (eg, divorce/disownment); limited knowledge of cancer and associated symptoms; and financial and access barriers associated with travel and appointments.ConclusionDue to variable quality of studies, future evaluations would benefit from using validated measures and robust study designs. The use of TCAM and gender influences appear to be important barriers to help-seeking in LMIC. Cancer awareness campaigns developed with LMIC communities need to address cultural influences on medical help-seeking behaviour.