Salix alba (SA), commonly known as white willow, is a plant used in folk medicine for the treatment of chronic and acute inflammation, infection, pain, and fever. The phytochemical characterization of the bark extract of this plant indicated that its main component is salicin, a precursor of the anti-inflammatory agent acetylsalicylic acid. Considering the lack of studies evaluating the genetic toxicity and cytotoxic action of SA bark extract on human cells, as well as the chemical characterization of its major phenolic compounds, the present study was designed to (1) investigate the cytotoxic and genotoxic potential of SA bark extract on human peripheral leukocyte cells and human hepatoma cell line HepG2, and (2) characterize its major phenolic constituents. The phenolic compounds found were salicylic acid, salicin, salidroside, saligenin, tremulodin, salicoylsalicin, salicortin, and tremulacin. The results using trypan blue staining test showed viability decreases (viability less than 70%) for concentrations of SA extract equal and higher to 200 µg/ml. Low genotoxic activity (comet assay) was exhibited for 50 and 100 µg/ml SA extract in human leukocytes. SA did not exert a marked clastogenic/aneugenic effect on leukocytes and HepG2 human cells. Data suggest that the genotoxic effects of SA bark extract occur when it is not metabolized by liver enzymes.