This study investigated the in vitro anticancer activities of a total of 14 wild angiosperms collected in Saudi Arabia. The cytotoxic activity of each extract was assessed against human breast adenocarcinoma (MCF-7) cell lines by using the MTT assay. Among the plants screened, the potential cytotoxic activity exhibited by the extract of Lavandula dentata (Lamiaceae) was identified, and we analyzed its anticancer potential by testing antiproliferative and apoptotic activity. Our results clearly show that ethanolic extract of L. dentata exhibits promising cytotoxic activity with an IC50 value of 39 μg/mL. Analysis of cell morphological changes, DNA fragmentation and apoptosis (using an Annexin V assay) also confirmed the apoptotic effect of L. dentata extract, and thus, our data call for further investigations to determine the active chemical constituent(s) and their mechanisms of inducing apoptosis.