Purpose: 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 alongside hepatorrhaphy vs. spleen autotransplantation as a patch on the liver parenchyma. Methods: A total of 24 rats were separated into two groups: the spleen autotransplantation on the omentum (SAO) and the liver (SAL). They underwent a uniform and simultaneous procedure involving full-thickness injuries to the left lobe of the liver and grade-four spleen injuries. We measured hemoglobin (Hb), white blood cell (WBC), complement (C3 and C4), and immunoglobulin G, M, and A (IgG, IgM, IgA) levels before and four weeks after the surgery. We utilized Technetium-99m scintigraphy to evaluate the post-transplant splenic graft functions four weeks after the surgery. Results: The two groups had no significant difference in the hematologic and immunologic factors before surgery. However, both procedures significantly reduced Hb, 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). Conclusions: 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.