Background: Delirium is a frequent and serious presentation for cancer patients. Here we review delirium detection in hospitalised adult oncology settings. Patients and Methods: MEDLINE, EMBASE, CINAHL, PsycINFO, and SCOPUS databases were searched from January,1996 to August, 2017. Key concepts were: delirium, cancer, in-patient oncology and delirium screening/detection. Results: Of 896 unique studies identified; 91 met full text review criteria. Of 12 eligible studies, four applied recommended case ascertainment to all patients, three used delirium screening tools alone or with case ascertainment tools sub-optimally applied, four used tools not recommended for delirium screening or case ascertainment, one used the Confusion Assessment Method with insufficient information to determine if it met case ascertainment status. Two studies presented delirium incidence rates; 7.8%, and 17% respectively. Prevalence rates ranged from 18-33% for general medical or oncology wards; 42-58% for Acute Palliative Care Units (APCU); and for older cancer patients: 22% and 57%. Three studies reported reversibility; 26% and 49% respectively (APCUs) and 30% (older patients with cancer). Six studies had low risk of bias according to QUADAS criteria; all studies in the APCU setting were rated at higher risk of bias. Tool selection, study flow and recruitment bias reduced study quality. Conclusion: The knowledge base for improved interventions and clinical care in adult oncology is limited by the low number of studies. A clearer distinction between screening and diagnostic tools is required to provide an improved understanding of the rates of delirium and its reversibility in this population. At present extrapolation from findings in other acute hospital settings, such as aged care, may help support selection of delirium screening for the oncology inpatient setting. Further validation of appropriate delirium tools is required in acute oncology settings to detect the presence and or resolution of delirium.