Inhibition of immune checkpoint proteins is effective in adult cancers but has shown limited efficacy in pediatric cancers. While factors regulating expression of immune checkpoint proteins such as PD-L1 are well-documented in adult cancers, their regulation is poorly understood in pediatric cancers. Here, we show that PD-L1 is upregulated in distinct subsets of Wilms tumor, the most common pediatric kidney cancer. Specifically, chemotherapy-exposed Wilms tumor specimens exhibited higher levels of PD-L1 expression, and common chemotherapeutics upregulated PD-L1 in childhood cancer cell lines in vitro. Furthermore, mutations in CTNNB1 and DROSHA, the two most commonly mutated genes in Wilms tumor, correlated with higher PD-L1. Activation of Wnt/β-catenin signaling and knockdown of DROSHA or DICER1 both increase PD-L1 in vitro. Lastly, in adult cancers, DICER1 alterations are associated with immune gene expression signatures and improved survival in response to immune checkpoint inhibitors. Together, our results identify clinical and biological properties regulating PD-L1 in Wilms tumor that may inform precision therapy approaches in pediatric immuno-oncology.