The purpose of this study undertaken in an acute care hospital was to evaluate sensitivity and specificity of the documentation of nurse-reported delirium symptoms in medical charts. This is a descriptive study based on the clinical assessments of a study nurse and nursing notes in the medical charts of 226 delirious older patients newly admitted to an acute care hospital. The results of this prospective validation study indicated that documentation of delirium symptoms is poor. Disorientation, agitation and altered level of consciousness were the three symptoms yielding a higher level of sensitivity, but even so said symptoms were reported in less than a third of the medical charts. Univariate analysis suggested that higher comorbidity level, more severe symptoms of delirium and the use of physical restraints were associated with more valid documentation of delirium symptoms in medical charts. Lastly, this study corroborates results of previous studies, indicating that documentation of delirium symptoms in medical charts can be improved. Future study should target improving nurse documentation of delirium symptoms in medical charts.