In this study, BALB/c mice with Ehrlich solid tumors were used to examine the effect of Achillea millefolium L. (AM) extract on the Ehrlich ascites tumor (EAT) model, which is one of the experimental cancer models. Also known as yarrow and plant, AM has antioxidant, anti-inflammatory, antibacterial and antitumor properties. In our study, 57 male BALB/c type mice, 8-10weeks old, weighing 25-30g, were used. Mice were divided into two groups. Ehrlich Solid Tumor group: Negative Control Group (ENC), Positive Control Group (EPC), and Treatment Group (TG) (TNCAM-200mg/kg, TPCAM-400mg/kg). EPC and TG were given to EAT cells. Each EAT contained 1 × 106 (will be 6 out of 10: so:000000) EAT cells, 0.1ml of phosphate-buffered saline (PBS) was administered subcutaneously (s.c.) to the nape of mice. Then It was awaited for solid tumor formation. AM extract was administered intraperitoneally (i.p.) to TG for 17days to mice. AM extract was found to have a curative effect on areas of inflammation, bleeding, and necrosis in treatment groups treated with AM extract alone. The treatment groups showed nearly normal histological results compared to the positive control group. According to the results, the TPCAM-400mg/kg group had a more significant histological impact than the TNCAM-200mg/kg group. In terms of tumor growth, tumor length, tumor volume, and tumor weight, AM extract did not show significant effects. However, in the light of histological findings, promising results of AM were observed in mice in which Ehrlich Solid Tumor was formed.