Abstract Background and Aims Presently, the clinical outcomes associated with IgA nephropathy exhibiting heavy proteinuria and the potential correlation between decreasing serum albumin levels and adverse prognosis have not been conclusively established. The present study was designed to elucidate the clinical and pathological characteristics of IgA nephropathy patients who present with nephrotic-range proteinuria, particularly in relation to serum albumin levels. Method This retrospective cohort study was conducted using data from biopsy-confirmed IgA nephropathy patients presenting with nephrotic-range proteinuria between 2017 and 2022 from eight university-affiliated hospitals in South Korea. Patients were stratified into two groups based on a serum albumin level of 3.0 g/dl. The study involved a comparative assessment of clinical and pathological characteristics across these two groups, as well as an evaluation of clinical prognosis with respect to the end-stage kidney disease (ESKD). Results The analysis included a total of 127 patients. Of these, 86 patients had a serum albumin level above 3.0 g/dl (designated as the preserved albumin group, or PA group), while 41 patients had levels below 3.0 g/dl (designated as the reduced albumin group, or RA group). The baseline characteristics of the two groups were found to be statistically similar. The mean age of the patients was 46.46 years, and 46.46% were male. In the laboratory findings, the RA group had significantly elevated erythrocyte sedimentation rate compared to the PA group. Additionally, total cholesterol and low-density lipoprotein-cholesterol levels were significantly higher in the RA group compared to the PA group. Proteinuria was observed to be significantly higher in the RA group. Pathological examinations demonstrated that in electron microscopy (EM) findings, the RA group exhibited a more pronounced diffuse foot process effacement. Over the course of one year, the trend in creatinine changes exhibited differences between the two groups over time (time x group interaction P = 0.002). Furthermore, it appeared that the reduction in the quantity of proteinuria was more substantial within the RA group (time x group interaction P = 0.001). During a median follow-up period of 25.22 months (ranging from 11.98 to 49.23 months), 14 patients (11.02%) in the PA group progressed to ESKD, compared with 10 patient (24.39 %) in the RA group. However, there was no statistically significant difference between the two groups in terms of progression to ESKD (P = 0.330). Conclusion In patients diagnosed with IgA nephropathy presenting with nephrotic-range proteinuria, a decline in serum albumin levels was associated with diffuse foot process effacement, and the decrease in serum albumin was not found to be associated with adverse prognosis.