Vinca sardoa (Stearn) Pignatti, known as Sardinian periwinkle, is widely diffused in Sardinia (Italy). This species contains indole alkaloids, which are known to have a great variety of biological activities. This study investigated the antileukemic activity against a B lymphoblast cell line (SUP-B15) of V. sardoa alkaloid-rich extracts obtained from plants grown in Italy, in Iglesias (Sardinia) and Rome (Latium). All the extracts showed a good capacity to induce reductions in cell proliferation of up to 50% at the tested concentrations (1–15 µg/mL). Moreover, none of the extracts showed cytotoxicity on normal cells at all the studied concentrations.