Abstract: Objective To understand the influence of nonthyroidal illness syndrome (NTIS) on mortality in the elderly male patients hospitalized for pulmonary infection. Methods Cross-sectional study was conducted in 239 male subjects aged 60 or over who were hospitalized for pulmonary infection from January 2012 to December 2013. All patients were divided into NTIS group and control group according to whether the patient was with NTIS or not. The differences in inflammatory markers, the correlation between inflammatory markers and T₃, and the influence of T₃ on survival were analyzed. Results There were statistically significant differences in WBC(8.2±4.0)×10⁹/L vs (6.8±2.4)×10⁹/L, P=0.008, neutrophil proportion (0.7%±0.1% vs 0.6%±0.1%, P=0.015, CRP (4.9±5.1) mg/L vs (2.6±2.8) mg/L, P=0.002, length of antibiotic use(34.8±29.2) d vs (20.9±20.7) d, P< 0.001 between NTIS group and control group. Pearson correlation analysis showed that there were negative correlations between TT3 and CRP (r=-0.258, P< 0.001), WBC (r=-0.207, P=0.001), neutrophil proportion (r=-0.184, P=0.004), length of antibiotic use (r=-0.196, P=0.002), between FT₃ and CRP (r=-0.264, P< 0.001), WBC (r=-0.199, P=0.002). The cumulative survival rate of NTIS group was significantly lower than that of control group (67.2% vs 79.4%, P=0.007). Multivariate Cox regression analysis showed that the overall mortality decreased with the increase of FT₃ and TT₃ levels after adjusting age (P< 0.05, respectively). Conclusion Patients with NTIS show more severe conditions and lower 2-year survival rate.