We have shown that plasminogen deficiency significantly suppresses atherosclerosis in low-density lipoprotein receptor (LDLR) and APOBEC1 double knockout (L^-/-/A^-/-) mice, a model of hyper-LDL cholesterolemia. Since tissue plasminogen activator (tPA) is involved in the activation of plasminogen, it is speculated that tPA may be involved in atherosclerosis. In this study, we investigated the effect of tPA on atherosclerosis. To determine the effect of tPA on atherosclerosis, LDLR, APOBEC1, and Plat triple knockout (L^-/-/A^-/-/Plat^-/-) mice were generated by crossing Plat knockout mice with LDLR and APOBEC1 knockout mice. The mice were fed a normal diet and kept for 24, 36, and 48 weeks, after which they were analyzed for atherosclerosis. Aortic sinus sections were stained with hematoxylin-eosin and Masson's Trichrome. The plaque lesion area in the aortic sinus was significantly smaller in L^-/-/A^-/-/Plat^-/- mice than in L^-/-/A^-/- mice. Furthermore, aortas were cut longitudinally and stained with Sudan IV. The plaque area in the aorta was significantly smaller in L^-/-/A^-/-/Plat^-/- mice than in L^-/-/A^-/- mice. These results suggest that tPA is involved in atherosclerosis.