The widespread use of plastics has led to a substantial increase in plastic waste, resulting in the dissemination of plastic debris throughout ecosystems and posing significant threats to biota. Bis(2-ethylhexyl) phthalate (DEHP), a commonly used plasticizer, enhances plastic flexibility but may also exert subtle toxic effects. This study aimed to investigate the potential toxicological impacts and underlying mechanisms of microplastics (MPs), di-(2-ethylhexyl) phthalate (DEHP), and their combined exposure (MPs + DEHP) on oxidative stress, apoptotic damage, transcriptomic alterations, and metabolic disturbances in mice. The results demonstrated that exposure to MPs, DEHP, and MPs + DEHP impaired the antioxidant defense system and reduced overall antioxidant capacity. Concurrently, all three exposure conditions significantly increased biochemical markers, particularly those associated with liver dysfunction, prompting further analysis of hepatic tissues. Histopathological examination revealed apoptotic damage in hepatocytes. Integrated transcriptomic and metabolomic analyses indicated that exposure to MPs, DEHP, and MPs + DEHP disrupted carbohydrate, amino acid, and lipid metabolism, induced the expression of genes related to hepatocarcinogenesis, and impaired purine metabolism. Moreover, MP and DEHP exposure aggravated hepatic apoptosis and inflammatory responses via activation of the PI3K/AKT signaling pathway, thereby eliciting notable biotoxic effects. These findings provide new scientific evidence regarding the individual and combined toxicological effects of MPs and the plastic additive DEHP on living organisms.