Objective To analyze the diagnostic value of serum levels of Wnt5a and soluble interleukin-2 receptor (sIL-2R) for elderly patients with type 2 diabetes mellitus (T2DM) complicated by pulmonary infection and their relationship with severity and prognosis of pulmonary infection.Methods The 84 elderly patients with T2DM and pulmonary infection who were treated in our hospital between January 2021 and December 2022 were selected as the observation group, 30 patients with T2DM who were hospitalized during the same period were selected as the diabetes mellitus group, and 30 healthy volunteers who came to the hospital for health checkup during the same period were selected as the control group. The levels of Wnt5a and sIL-2R were compared among the three groups, and receiver operating characteristic (ROC) curve was drawn to assess the diagnostic value of levels of Wnt5a and sIL-2R for elderly patients with T2DM and pulmonary infection. Pearson correlation analysis was performed to determine the correlations of the levels of Wnt5a and sIL-2R with other laboratory indicators of patients within the observation group. The patients in the observation group were further divided into mild, moderate and severe subgroups according to the severity of pulmonary infection, and the levels of Wnt5a and sIL-2R were compared among the three subgroups. According to the prognosis, the patients in the observation group were divided into the rehabilitation subgroup and the death subgroup, and the levels of Wnt5a and SIL-2R were also compared between the two subgroups.Results The levels of Wnt5a, sIL-2R, and FPG were higher (P < 0.05), and FEV1 was lower in the observation group and the diabetes mellitus group compared with the control group (P < 0.05). The level of sIL-2R was higher (P < 0.05), and FEV1 was lower in the observation group than in the diabetes mellitus group (P < 0.05). A total of 98 strains of pathogens were detected in 84 patients, among which Gram-positive bacteria were the most prevalent (50.00%), followed by Gram-negative bacteria (47.96%) and fungi (2.04%). The area under the curve (AUC) and the sensitivity of the combined detection were the highest, being 0.935 (95% CI: 0.873, 0.973) and 85.71% (95% CI: 0.760, 0.921), respectively. The specificity of sIL-2R was the highest, being 93.33% (95% CI: 0.765, 0.988). Pearson correlation analysis revealed that the levels of Wnt5a and sIL-2R were negatively correlated with FEV1 (r = -0.228 and -0.227, both P < 0.05) and positively correlated with the level of FPG (r = 0.450 and 0.647, both P < 0.05). Compared with mild subgroup, the levels of Wnt5a and sIL-2R in the severe subgroup were higher (P < 0.05), and the level of sIL-2R in the moderate subgroup was higher (P < 0.05). The level of sIL-2R in the severe subgroup was higher than that in the moderate subgroup (P < 0.05). Compared with the rehabilitation subgroup, the levels of Wnt5a and sIL-2R were higher in the death subgroup (P < 0.05).Conclusion Serum levels of Wnt5a and sIL-2R are elevated in elderly patients with T2DM complicated by pulmonary infection, and are to some extent correlated with pulmonary function and blood glucose of patients. They could assist in clinically assessing whether patients with T2DM have pulmonary infection and the severity of pulmonary infection, and predicting the prognosis.