Aim To examine factors predicting the onset of perioperative delirium and acute exacerbation of behavioral and psychological symptoms of dementia (BPSD), based on patient background, operative background and laboratory data obtained on admission, in elderly patients with proximal femoral fracture. Methods The participants were 152 patients (aged >70 years) who underwent surgery between 1 November 2012 and 31 March 2014. The participants were classified into group B (with onset of perioperative delirium or acute exacerbation of BPSD, n = 52), or group N, (without onset, n = 100), and risk factors were retrospectively examined. Onset was judged based on the presence or absence of common items; that is, “hallucination and delusion,” “disturbing speech,” “excitatory behavior” and “altered sleep‐wake cycle.” The participants were observed for 1 week after admission. Results The incidence of perioperative delirium or acute exacerbation of BPSD was 34.2% in total. In univariate analysis, the incidence was significantly higher (P < 0.005) in group B for the age, history of dementia and serum albumin level items. In multivariate analysis, history of dementia, serum albumin level and peripheral lymphocyte count (odds ratio 3.55, 0.17, 1.00, respectively) were identified as independent predictive factors. In the subanalysis, the incidence was 91.3% in the group with a history of dementia, serum albumin level <3.7 g/dL and peripheral lymphocyte count < 1200/μL. Conclusions History of dementia, a low serum albumin level and low peripheral lymphocyte count were found to be useful factors for predicting the onset of perioperative delirium and acute exacerbation of BPSD. Geriatr Gerontol Int 2016; 16: 821–828.