Doxorubicin (DOX) is a potent cytotoxic chemotherapeutic agent limited in clinical application owing to its cumulative and irreversible cardiotoxicity. Circ_0001312 is highly expressed in patients with heart failure. However, it is still unclear whether circ_0001312 plays any roles in DOX-induced cardiotoxicity.Human AC16 cardiomyocytes in functional group were stimulated with DOX. The levels of genes and proteins were detected by qRT-PCR and western blotting. The proliferation, apoptosis, as well as inflammatory and oxidative injury in cardiomyocytes were investigated. Dual-luciferase reporter, RNA immunoprecipitation, and pull-down assays were utilized to confirm the binding between miR-409-3p and circ_0001312 or HMGB1 (high-mobility group box 1). Exosomes were isolated by using the commercial kit and identified by transmission electron microscopy (TEM) and nanoparticle-tracking analysis (NTA).DOX impaired cardiomyocyte proliferation and induced apoptotic, inflammatory, and oxidative injury in cells. Furthermore, it promoted circ_0001312 expression, and the knockdown of circ_0001312 could reverse DOX-evoked cardiomyocyte injury. In terms of mechanics, circ_0001312 bound competitively to miR-409-3p to up-regulate HMGB1, which was a target of miR-409-3p. DOX decreased the miR-409-3p but increased the HMGB1 expression in cardiomyocytes. Functionally, miR-409-3p inhibition attenuated the protective action of circ_0001312 silencing on cardiomyocytes under DOX treatment. Moreover, miR-409-3p could abate DOXevoked apoptosis, and inflammation and oxidative stress in cardiomyocytes, and these effects were counteracted by HMGB1 overexpression. In addition, circ_0001312 was secreted by exosomes and could be transmitted via exosomes.Circ_0001312 reversed the cytotoxic effects mediated by DOX on cardiomyocytes via the miR-409-3p/ HMGB1 axis. Besides, it was released to the extracellular space by exosomes.