Alzheimer’s disease is the leading cause of dementia, marked by progressive cognitive decline and neuropsychiatric disturbances collectively known as behavioral and psychological symptoms of dementia (BPSD). Plasma phosphorylated tau at threonine-181 (pTau181) has emerged as a minimally invasive biomarker of tau-related neurodegeneration, but its association with BPSD remains uncertain. This study investigated the relationship between plasma pTau181 levels and BPSD in Alzheimer’s dementia. An analytical observational study with a cross-sectional design was conducted in patients clinically diagnosed with predefined eligibility criteria. Plasma pTau181 concentrations were measured using enzyme-linked immunosorbent assay (ELISA), while BPSD was assessed using the Neuropsychiatric Inventory Questionnaire (NPI-Q). Statistical analyses were performed to examine associations between plasma pTau181 and BPSD status. Plasma pTau181 levels ranged from 4.32 to 97.23 pg/mL, with a median plasma pTau181 level of 19.29 pg/mL (IQR: 11.81-25.05) in patients without BPSD and 20.67 pg/mL (IQR: 11.81-43.41) in those with BPSD. No significant differences in pTau181 levels were observed between patients with and without BPSD (p = 0.310). These findings suggest that plasma pTau181 may not be directly related to the presence of BPSD in Alzheimer’s dementia. While plasma pTau181 remains a promising biomarker of tau pathology, its predictive value for neuropsychiatric symptoms appears limited. Longitudinal studies are needed to explore its role in BPSD pathophysiology further.