Pain assessment in older individuals with cognitive impairment is challenging. Evidence on the performance of pain assessment tools in this population remains limited. The aim of this study was to evaluate the performance of self-reported pain, nurse-reported pain, and observational pain tools among older patients with cognitive impairment using a prospective observational design. In all, 152 older individuals admitted to the acute geriatric ward were recruited through convenience sampling. Three methods of pain assessment were compared: self-reported pain (SRP), observational pain using the Pain Assessment in Advanced Dementia (PAINAD) tool, and nurse-reported pain (NRP). Cognition and mood were assessed with the Mini-Mental State Examination (MMSE) and the 15-item Geriatric Depression Scale (GDS-15). There was moderate agreement between SRP and PAINAD (k = 0.438) and fair agreement between SRP and NRP (k = 0.263). There was statistically significant correlation between SRP and GDS-15 (r = 0.382, p