Objective To investigate the correlation of peripheral blood monocyte percentage and count with behavioral and psychiatric symptoms of dementia (BPSD) in patients with Alzheimer disease (AD). Methods A total of 74 AD patients admitted in our department from January to October 2018 were recruited in this study. According to the results of neuropsychiatric inventory (NPI), they were divided into BPSD group (n=37) and non-BPSD group (control, n=37). Their venous blood samples were harvested at administration and in 1 month after treatment for monocyte percentage and count. SPSS statistics 19.0 was used to perform the stati-stical analysis. Student′s t test or Chi-square test was employed for comparison between groups, and Spearman correlation analysis was applied for the relationship. Results The BPSD group had significantly higher monocyte percentage [(8.56±0.92)% vs(5.36±0.32)%, (5.54±0.41)% vs (5.33±0.33)%] and count [(0.60±0.06)×10⁹/L vs (0.36±0.04)×10⁹/L, (0.38±0.03) vs (0.35±0.04)×10⁹/L] than the non-BPSD group at administration and in 1 month of treatment (P<0.05). The monocyte percentage (r=0.903) and count (r=0.729) were both positively correlated with NPI score. Conclusion The BPSD is correlated with monocyte percentage and count in peripheral blood of AD patients.