Breast and cervical cancer represent a major problem of women's global public health. Here, we investigated the chemical composition of essential oils from leaves and flowers of T. ostenii and the antineoplastic potential in a cervical cancer and breast cancer cell line, SiHa and MCF-7; and non-tumoral cells, HaCat. The chemical analysis revealed a predominance of oxygenated monoterpenes in both essential oils. The IC50 after 24 h of treatment was 72 ng/mL for EO 1 and 83 ng/mL for EO 2 in SiHa cells. For MCF-7 the IC50 was 174.3 ng/mL for EO 1. For HaCat cells it was 54.45 ng/mL for EO 1 and 20.83 ng/mL for EO 2. A synergistic effect with both essential oils and cisplatin was also verified. SiHa cells had their wound healing capacity reduced after 48 h of treatment with EO 2 and both essential oils were able to significantly inhibit the adhesion process and clonogenic ability after 24 h of treatment. Our results suggest a long-lasting inhibitory activity in SiHa cells because of the low recovery capacity of cells after treatment withdrawal. Flow cytometer with annexin V/propidium iodide demonstrated a majority cell death through late apoptosis after 24, 48 and 72 hours of treatment.