Background <p>Wilms tumor (WT) is the most common renal tumor in children, with prognosis varying widely due to multiple factors. This study aims to identify key prognostic factors in WT, with a particular focus on pathological grade.</p> Methods <p>We retrospectively analyzed 186 WT patients diagnosed between 2000 and 2021 using SEER database. Clinical and pathological factors such as age, tumor grade, and SEER stage were assessed for their impact on overall survival (OS) and cancer-specific survival using Cox regression models. The SEER stage was categorized as localized, regional, or distant. A nomogram was developed based on these factors to predict 1-, 3-, and 5-year OS, and its predictive accuracy was evaluated.</p> Results <p>Of the total, 94 patients had grade I-III tumors, while 92 had grade IV tumors. Univariate analysis revealed that older age (<i>p</i> &lt; 0.001), higher grade (<i>p</i> = 0.011), distant metastasis (<i>p</i> &lt; 0.001), and larger tumor size (<i>p</i> = 0.025) were associated with poorer prognosis. Multivariate analysis confirmed age at diagnosis (<i>p</i> &lt; 0.001), tumor grade (<i>p</i> = 0.008), and stage (<i>p</i> = 0.004) as independent prognostic factors for OS. In the grade IV subgroup, patients had a higher rate of distant metastasis (37.0%), which significantly worsened their prognosis (<i>p</i> = 0.004). The nomogram demonstrated a strong predictive accuracy, with a C-index of 0.796 and AUC values of 0.886, 0.790, and 0.835 for predicting 1-, 3-, and 5-year overall survival, respectively. Calibration and decision curve analyses further validated the model’s reliability.</p> Conclusion <p>WT prognosis is closely associated with age, tumor grade, and SEER stage. The nomogram developed in this study serves as a reliable tool for predicting long-term survival in WT patients, aiding in clinical management and personalized treatment strategies.</p>