Immunoglobulin A (IgA) nephropathy is the most prevalent primary chronic glomerular disease worldwide. The autoimmune response caused by galactose-deficient polymeric IgA1 is the original mechanism triggering the IgA nephropathy. Significant research advances in pathogenesis and biomarkers of IgA nephropathy have been made in recent years and provide the basis for noninvasive diagnosis, monitoring of disease activity, and disease-specific therapies. The research advances in molecular mechanisms and key serum biomarkers in the pathogenesis of IgA nephropathy are reviewed in this paper.