Wilms' tumor 1-associated protein (WTAP), a component of the m6A methyltransferase complex, recruits the m6A methyltransferases METTL3 and METTL14 to the corresponding mRNA targets to participate in the formation of N6-methyladenosine. However, the molecular mechanism of WTAP in the tumorigenesis and progression of nasopharyngeal carcinoma (NPC) remains unclear. This study aimed to explore the prognostic value and biological function of WTAP in NPC. We assessed WTAP expression and its prognostic significance using microarray datasets from the Gene Expression Omnibus (GSE12452) database and 100 NPC tissues via bioinformatics analysis and immunohistochemistry (IHC), respectively. Moreover, gene ontology (GO) and gene set enrichment analysis (GSEA) were performed. In addition, the correlation of WTAP expression with the expression of immune cell biomarkers was analyzed. The results showed that WTAP expression was significantly overexpressed in NPC tissues in GSE12452. The overexpression of WTAP was validated by the external datasets including NPC tissues (GSE150430) and NPC cell lines (GSE39826). GO analysis suggested enrichment in the nucleoplasm (cellular component) and cell cycle (biological process). The GSEA revealed that differentially expressed genes were enriched in E2F-targets, Myc_targets_v1, G2M checkpoint, Myc_targets_v2, and Interferon-alpha-response. In IHC analysis, WTAP was upregulated in NPC tissues, and high levels of WTAP expression were significantly correlated with the advanced T stage (p=0.047) and advanced N stage (p=0.018). Cox regression demonstrated that WTAP overexpression was an independent biomarker of poor prognosis for overall survival (hazard ratio [HR], 4.747; 95% confidence interval [CI], 1.671-13.482; p=0.003). In IHC analysis, the expression of WTAP was positively correlated with CD206 (biomarker for M2 macrophages) (p=0.018) but negatively correlated with CD8a (biomarker for cytotoxic T cells) (p=0.001). In conclusion, WTAP is a promising prognostic biomarker and may participate in the regulation of immune cell infiltration in NPC.