In vitro models are often used to study the functions of macrophages, including the process of phagocytosis. The use of primary macrophages has limitations associated with the individual characteristics of animals, which can lead to insufficient standardization of the results obtained. This disadvantage is lacking in immortalized cell lines. The PMJ2-R cell line was derived from in vivo immortalization and retains many of the primary peritoneal macrophages functions, but little is known about its differences from normal cells. In this article, we carried out a comparative analysis of the proteomes of PMJ2-R cells and primary peritoneal macrophages isolated from the C57BL/J6 mice. Particular attention was paid to the analysis of proteins involved in the process of phagocytosis. A total of 4005 proteins were identified, of which 797 were quantified. Our results indicate that there are significant differences in the abundance of a large number of proteins, including important proteins associated with the process of phagocytosis, such as Elmo1, Gsn, Hspa8, Itgb1, Ncf2, Rac2, Rack1, Sirpa, Sod1, C3, Msr1. Thus, when using PMJ2R cells as model cells in the study of the peritoneal macrophages functions, features revealed in this study should be taken into account.