Purpose <p>Although the DLGAP4 gene is well-established in neurological disorders, its function in hepatocellular carcinoma (HCC) remains unclear. This study aims to characterize DLGAP4 expression patterns, prognostic significance, and association with immune infiltration in the HCC tumor microenvironment, to assess its potential as a biomarker or therapeutic target.</p> Methods <p>We analyzed DLGAP4 expression in HCC and its prognostic significance using the TCGA database, performing survival analysis with the Kaplan-Meier method. Functional pathways linked to DLGAP4 were identified via GO and KEGG enrichment analyses, and further explored by gene set variation analysis (GSVA). Immune cell infiltration correlations were assessed using TIMER2.0. Clinical samples were immunohistochemically stained to validate bioinformatic results.</p> Results <p>DLGAP4 expression was significantly upregulated in HCC tissues and associated with poor patient prognosis. Enrichment analysis implicated DLGAP4 in biological processes including chromatin modification and protein translation. Single-cell data analysis revealed that high DLGAP4 expression correlated with features of the tumor microenvironment, such as tumor-associated macrophages, stemness, angiogenesis, and metabolic reprogramming. Immunohistochemical results further confirmed a significant correlation between DLGAP4 expression and immune cell infiltration.</p> Conclusions <p>DLGAP4 is upregulated in HCC and associated with poor prognosis and immune infiltration in the tumor microenvironment, suggesting its potential as a prognostic biomarker and therapeutic target for HCC.</p>