Background: ATP7B encodes a copper-transporting adenosine triphosphatase that maintains intracellular copper ion homeostasis by transporting excess copper ions from the cell into the bile. The main objective of this study was to investigate the relationship between ATP7B and various cancers, to reveal its potential role in cancer progression, modulation of the tumour immune microenvironment. To provide comprehensive insights into the relationship between this gene (ATP7B) and cancer by understanding the associated pathological mechanisms. We expect to explore its potential as a prognostic biomarker for cancer and propose new insights for immunotherapy strategies for cancer. Methods: The potential function of ATP7B in multiple cancers was investigated using information from The Cancer Genome Atlas (TCGA), Genotype-Tissue Expression (GTEx), Tumor Immune Estimation Resource version 2 (TIMER 2.0), Kyoto Encyclopedia of Genes and Genomes (KEGG), and Human Protein Atlas (HPA). Variations in ATP7B expression, mutations, DNA methylation, immunohistochemistry, survival, pathological stage, immune cell infiltration, drug response and single-cell biological functioning condition were examined. Results: A wide variety of cancer types showed high levels of ATP7B expression. In the majority of malignancies, the presence of ATP7B expression in tumor tissues has been associated with better overall survival and disease-free survival rates. Cases of UCEC and BLCA with altered ATP7B have improved prognoses. Most tumors had higher levels of DNA methylation. ATP7B was linked to numerous immune cells, genes, and tumor immunity in several cancers. ATP7B expression levels correlate with suppression of the tumour immune microenvironment; this is demonstrated by a negative correlation with CD8+ T cell infiltration in various malignancies. ATP7B-overexpressing patients with immune checkpoint inhibitors have a better prognosis. Conclusions: Our research provides a thorough understanding of ATP7B’s oncogenic function in various tumor types. Our findings imply that ATP7B may be a biomarker for the prognosis of cancer patients. Better prognosis for tumour patients will be achieved through the use of immune checkpoint inhibitors and by interfering with ATP7B expression levels which brings new insights into tumour therapy.