It has been suggested that right-sided and left-sided colorectal cancer may arise by different mechanisms. However, there have been few studies of mucinous adenocarcinoma (MA) in relation to location. Therefore, we analyzed clinicopathological characteristics, microsatellite instability (MSI), and expression of MUC1, MUC2, MUC5AC mucin core proteins, and p53 by immunohistochemistry in relation to tumor location. Ninety-six consecutive colorectal MAs and ninety-eight nonmucinous adenocarcinomas (nMAs) were investigated. Right-sided MAs, by comparison with those on the left side, were characterized by older age, larger tumor size, lower stage at presentation, peritumoral lymphocytic response, background of serrated adenoma, MSI-H phenotype, higher MUC2 and MUC5AC expression, and lower p53 protein overexpression. Right-sided nMAs, relative to those on the left side, were associated with MSI-H phenotype, higher MUC2 and MUC5AC expression, and lower p53 protein overexpression. Thus, MSI-H phenotype, expression of MUC2 and MUC5AC, and infrequent p53 protein overexpression are associated with right-sided location as well as mucinous histology. In univariate analysis, right-sided location had a favorable effect on disease specific survival of the patients with MA, although it is not an independent predictor of survival. Our results indicate that MA is a distinctive form of colorectal cancer and has different phenotypes depending on tumor location.