The human gene microcephalin (MCPH1) plays a key role in DNA damage-induced cellular responses and chromosome condensation. Recent clinical studies proposed MCPH1 as a tumor suppressor gene in lung cancer, pancreatic cancer, and breast cancer, yet its roles remain poorly understood in other types of tumors. Pan-cancer analyses of MCPH1 are urgently required to help us understand the potential molecular functions of MCPH1 in other types of tumors. Here, we used several bioinformatic database and tools, including TCGA, GEO, ONCOMINE, and Human Protein Atlas to investigate the role of MCPH1 in 33 tumor types. We found that the expression of MCPH1 in tumor cases and normal cases were significantly different, and the higher expression of MCPH1 generally predicted poor overall survival for tumor patients, such as acute myeloid leukemia, liver hepatocellular carcinoma, and pancreatic adenocarcinoma. Meanwhile, lower expression of the MCPH1 gene was related to poor OS prognosis for KIRC and gastric cancer. Moreover, the expression level of MCPH1 was highly associated with the immune microenvironment. Our result provides some fresh light into the oncogenic roles of MCPH1 in various human cancers and revealed that MCPH1 may be a potential diagnostic and prognostic marker in LAML, PAAD, and gastric cancer.