In this study, doxorubicin (DOX)-loaded long circulating liposomes combined with curcumin (CUR) (DOX-CUR-LCLs) were successfully prepared as a novel formulation for cancer treatment. The particle size and distribution, zeta potential, drug loading capacity, and entrapment efficiency (EE) of the preparation were characterized. The in vitro anti-tumor activities of DOX-CUR-LCLs and DOX-LCLs against A549 cells were then evaluated and compared with that of free DOX. Cytotoxicity evaluation showed that DOX-CUR-LCLs had a significantly higher antitumor activity than other DOX preparations. These results suggest that novel DOX-CUR-LCLs, combination of DOX and CUR administered in long-circulating liposomes, could improve antitumor activity.