Use of natural products as an alternative medicine to treat cancer is increasing among people in Malaysia. Extracts of the herb Goniothalamus umbrosus (Kenerak) reportedly have cytotoxic and antiproliferative effects on breast, colon, kidney, leukemia, and pancreatic carcinoma cells, but scientific data are lacking. The goals of this study were to evaluate the phytochemical properties of the methanol extract of G. umbrosus leaves (GU-ML) to determine its antiproliferative effect on cervical cancer (HeLa) cells. Gas chromatography-mass spectrometry identified ten major phytochemical compounds present in the extract. The antiproliferative activities (IC50 values) of the extracts were 45.31ug/ml and 48.44ug/ml as determined by the alamarBlue® and MTS assays, respectively. Morphological changes in cells treated with the extract included cell shrinkage, rounding of cells, vacuolization, and cell elongation, all of which indicate apoptosis. Overall, these data illustrate the antiproliferative effects of the GU-ML on cervical cancer.