Kidney damage is common in patients with diabetes mellitus (DM). However, whether the type of kidney damage can be reliably diagnosed using clinical data alone remains unclear. Predictive factors for diabetic nephropathy (DN) outcomes are also poorly understood. In this study, the clinical manifestations of 111 cases of biopsy-proven DN were described, and the clinical and pathological parameters of patients with different DN outcomes were compared. Results showed that long DM duration (>10 years in 32.4% of patients), severe proteinuria (62.2%), and renal dysfunction (estimated glomerular filtration rate [eGFR]<60 mL/(min·1.73 m²)) (52.3%) did not accurately indicate whether the condition of these patients progressed to DN. Hematuria (48.6%) failed to specify either DN or nondiabetic renal disease. Diabetic retinopathy (78.4%) was a crucial complication in patients with DN. Kaplan–Meier analysis revealed that the renal survival of 53 patients who were diagnosed with DN and were followed up was not significantly associated with glomerular classification (P>0.05). Cox’s regression analysis demonstrated that renal survival time was significantly influenced by sex (b= 1.394, P= 0.038), hematuria (b= 0.036, P= 0.029), and eGFR (b= −0.039, P= 0.002) but was not significantly affected by age, 24 h urinary protein excretion, or glomerular classification (P>0.05). In conclusion, the clinical characteristics of DN vary, and renal biopsy is necessary to determine renal damage patterns. Sex, hematuria, and the eGFR may affect DN outcomes, whereas the glomerular classification may not.