Objective <p>To investigate the distribution characteristics of peripheral blood lymphocyte subsets in elderly psoriasis patients and analyze the interactions between immunosenescence and psoriasis and their impact on immune cell subpopulations.</p> Methods <p>This cross-sectional study enrolled 318 psoriasis patients and 167 healthy controls, stratified by age into elderly (≥ 65 years) and non-elderly (18–64 years) groups. Peripheral blood lymphocyte subsets, including CD3⁺ T cells, CD4⁺ T cells, CD8⁺ T cells, B cells, and NK cells, were analyzed using four-color flow cytometry. Generalized linear models were employed to analyze associations between PASI scores and lymphocyte subsets, and correlation network analysis was constructed to evaluate interaction patterns among immune cell populations.</p> Results <p>The elderly psoriasis group demonstrated significantly reduced CD8⁺ T cell percentage compared to controls (24.52% vs. 28.62%, <i>P</i> &lt; 0.001), accompanied by an elevated Th/Ts ratio (1.57 vs. 1.27, <i>P</i> &lt; 0.001) and significantly increased NK cell percentage and absolute count. Generalized linear modeling revealed a significant negative interaction effect between psoriasis and age on CD8⁺ T cell percentage (β = -3.979, <i>P</i> = 0.019), while the Th/Ts ratio exhibited a significant positive interaction effect (β = 0.230, <i>P</i> = 0.010). B cell absolute count showed a positive correlation with PASI score (<i>r</i> = 0.180, <i>P</i> = 0.001), with this correlation being more pronounced in elderly patients (<i>r</i> = 0.308, <i>P</i> = 0.014). Network analysis demonstrated reduced connectivity density among immune cell subpopulations in elderly patients.</p> Conclusions <p>Elderly psoriasis patients exhibit age-related alterations in peripheral blood lymphocyte subset distribution, characterized by decreased CD8⁺ T cells, elevated Th/Ts ratio, and increased NK cells. B cells may serve as potential biomarkers for assessing disease severity in elderly psoriasis patients.</p>