Abstract Background Delirium is a common geriatric syndrome, but only few studies have been done in nursing home residents. Therefore, the aim of this study was to investigate (point) prevalence of and risk factors for delirium in nursing homes in Belgium. Methods A multisite, cross-sectional study was conducted in six nursing homes in Belgium. Residents of six nursing homes were screened for delirium. Exclusion criteria were coma,‘end-of-life’ status and residing in a dementia ward. Delirium was assessed using the Delirium Observation Screening Scale. Results 338 of the 448 eligible residents were included in this study. Of the 338 residents who were evaluated, 14.2 % (95 %CI:3.94–4.81) screened positive for delirium with the Delirium Observation Screening Scale. The mean age was 84.7 years and 67.5 % were female. Taking antipsychotics (p = 0.009), having dementia (p = 0.005), pneumonia (p = 0.047) or Parkinson’s disease (p = 0.03) were more present in residents with delirium. The residents were more frequently physically restrained (p = 0.001), participated less in activities (p = 0.04), had had more often a fall incident (p = 0.007), had lower levels of cognition (p < 0.001; MoCA ≥ 26, p = 0.04; MoCA ≥ 25, p = 0.008) and a higher “Activities of Daily Living” score (p = 0.001). In multivariable binary logistic regression analysis, a fall incident (2.76; 95 %CI: 1.24–6.14) and cognitive impairment (OR: 0.69; 95 %CI: 0.63–0.77) were significantly associated with delirium. Conclusions Delirium is an important clinical problem affecting almost 15 % of the nursing home residents at a given moment. Screening of nursing home residents for risk factors and presence of delirium is important to prevent delirium if possible and to treat underlying causes when present.