Background: Schinus molle Linn. (Anacardiaceae) is a medicinal plant used by traditional healers in Mexican traditional medicine as antitumoral. Objective: This study was undertaken to obtain information that support the traditional use of the leaves from S. molle as antitumoral. Material and Methods: Antilymphoma properties of the ethanol extract of the leaves from S. molle (EELSm) and rutin were made on athymic CD-1 nu/nu and CD-1 mice inoculated with U-937 cell line (human leukemic monocyte lymphoma [HLML]), and for their antiproliferative effects on U-937 cell line by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Furthermore, the extract and rutin were tested for brine shrimp (BS) toxicity test. In addition, HPLC analysis was realized to known the content of rutin in the leaves from S. molle. Results: An EELSm and rutin exhibited important cytotoxic effects on U-937 cells line (IC50from 172.0 μg/mL and 9.6 μg/mL, respectively) and showed in vivo antitumoral properties on HLML in two murine models (EC50from 52.2 and 9.5 mg/kg to CD-1 nu/nu mice; EC50from 99.4 mg/kg and 6.8 mg/kg to CD-1 mice, respectively). In addition, both showed strong lethality on BS larvae (LC50≤ 22.2 μg/mL). The result of HPLC showed that rutin was the major constituent of EELSm. Conclusions: These test results support traditional medicinal use of S. molle as antitumoral and also suggest that both rutin and EELSm possess antitumor effect on HLML in murine models. Finally, rutin may play an important role in anticancer properties of S. molle. Abbreviations used: EELSm: Ethanol extract of the leaves from S. molle, HLML: Human leukemic monocyte lymphoma, HPLC: High pressure liquid chromatography, BS: Brine shrimp, BSLT: BS lethality test, DMSO: Dimethyl sulfoxide, MTT: 3 (4,5 dimethylthiazol 2 yl) 2,5 diphenyltetrazolium bromide