Colorectal cancer is the third most common cancer in the world. Due to the side effects of common treatments such as chemotherapy and radiotherapy, the use of herbal medicines has received much attention. Artemether (ARM) is an herbal medicine derived from artemisinin, which has many anti-tumor properties. However, factors such as low solubility and short half-life have limited the use of artemether in clinical practice. In this study, we aimed to reduce these limitations by encapsulating artemether in human serum albumin (HSA). The hydrodynamic diameter and the zeta potential value of ARM-ALB nanoparticles (NPs) were 171.3 ± 5.88 nm and −19.1 ± 0.82 mV, respectively. Comparison of the effect of free and encapsulated artemether on CT 26 cell line showed that the use of artemether in capsulated form can reduce the effective concentration of the drug. Additionally, in vivo studies have also shown that albumin–artemether nanoparticles can control tumor growth by increasing the production of cytokine IFN-γ and decreasing the production of IL4. Therefore, ARM-ALB nanoparticles have greater anti-tumor effects than free artemether.