Morinda citrifolia (MC) and Annona muricata (AM) are popularly used for the treatment of several diseases, including cancer. Our objective was to evaluate the effects of the juice of the MC fruit, and the ethanolic extract of AM leaves on Erhlich tumor cells, in mice and in vitro fibroblastic cells. The animals were divided into G1 and G2: controls; G3: treated with AM, and G4 juice: treated with MC. The animals were subjected to intraperitoneal inoculation of 103 tumor cells and then treated with the plants. G1 and G2 received a saline solution. Cells were grown in RPMI 1640 medium, supplemented with 10% fetal bovine serum, and maintained at 37°C in 5% CO2 atmosphere. After growth, the cells were trypsinized and incubated again. Subsequently, serial dilution of extracts and juice was performed and incubated again for 48 h. We evaluated the ascites growth, the survival rate, and cytotoxicity in fibroblast cells. AM and MC did not interfere in the ascites pattern. MC, but not AM showed significance in the survival rate. Both AM and MC produced cytotoxicity activity in T3T cells. Despite advances in medicine, cancer is still one of the leading causes of death in the world and traditional medications are not always effective. The use of MC may bring beneficial effects to patients since they interfere with different mechanisms of action during carcinogenesis. However, we suggest that further investigations should be performed.