In a simulated situation of simultaneous spleen and liver trauma, we aimed to compare the outcomes of treating both injuries with spleen autotransplantation on the omentum (SAO) alongside hepatorrhaphy versus spleen autotransplantation as a patch on the liver parenchyma. A total of 24 rats were separated into two groups: the SAO and the spleen autotransplantation on the liver. They underwent a uniform and simultaneous procedure involving full-thickness injuries to the left lobe of the liver and grade 4 spleen injuries. We measured hemoglobin, white blood cell (WBC), complement (C3 and C4), and immunoglobulin G, M, and A (IgG, IgM, IgA) levels before and 4 weeks after the surgery. We utilized Technetium-99m scintigraphy to evaluate the posttransplant splenic graft functions 4 weeks after the surgery. The two groups had no significant difference in the hematologic and immunologic factors before surgery. However, both procedures significantly reduced hemoglobin, C3, IgG, and IgA levels (all P<0.05). WBC counts significantly increased in the SAO group, whereas the IgM level decreased after the intervention (P<0.05). WBC was increased in the SAO group, while IgM and IgA were decreased in the SAO group. The Technetium uptake was similar between the two groups (P=0.3). In simultaneous spleen and liver injuries, the autotransplantation of splenic into the liver parenchyma appears to be a promising surgical approach for preserving spleen function and hepatorrhaphy at the same time instead of doing them separately.