BACKGROUND: The Wilms' tumor suppressor gene (WT1) is a critical regulator in kidney development and disease pathogenesis. With the identification of at least 36 isoforms in mammals, each potentially playing distinct roles, WT1's complexity is becoming increasingly apparent. The -KTS and +KTS isoforms, in particular, have been implicated in DNA and RNA regulation, respectively. This review consolidates recent insights into WT1's multifaceted role in renal morphogenesis and its implications in kidney diseases. SUMMARY: Our review highlights WT1's expression during embryonic kidney development and its maintenance in postnatal kidney function. We discuss the association of WT1 mutations with genetic nephropathies like Denys-Drash and Frasier syndromes, emphasizing its genetic significance. Additionally, we explore the implications of WT1 expression alterations in glomerular diseases, such as IgA nephropathy and lupus nephritis, where its role extends beyond a mere biomarker to a potential therapeutic target. KEY MESSAGES: The WT1 gene and its protein products are central to understanding kidney morphogenesis and the molecular basis of renal disorders. As our understanding of WT1's regulatory mechanisms expands, so does the potential for developing targeted therapies for kidney diseases. This review calls for further research to elucidate the precise functions of WT1 isoforms and to explore the upstream regulators of WT1 that could offer novel treatment strategies for kidney pathologies. The significance of WT1 in intricate signaling pathways governing kidney health and disease is underscored, highlighting the need for continued investigation into this pivotal gene.