Traditional medicine is currently being explored and developed widely by various countries because its cost effectiveness and reduced side effects. The green betel (Piper betle Linn.) and the red betel (Piper crocatum Ruiz and Pav.) are plants from the same Piper genus that are widely cultivated in Indonesia and have various phytochemical properties and pharmacological effects. The objective of this research is to determine the cytotoxicity of green leaves and red betel leaves. This research was conducted in two main stages: first, the extraction and preparation through the soxhletation method; second, a cytotoxicity test through the brine shrimp (Artemia salina Leach) lethality test (BSLT). The results showed that there were lethal concentration 50 % (LC50) value in both green betel leaves ethanolic extract and red betel leaves ethanolic extract, with 44.975 μg per mL and 31.556 μg per mL, respectively. The red betel (leaves ethanolic extract has a higher cytotoxicity than green betel (leaves ethanolic extract which can be seen from the lower lethal concentration of 50% (LC50) value. The difference in cytotoxicity is due to differences in plant varieties that cause variations in phytochemical content which affects the pharmacological effects. The green betel leaves ethanolic extract and the red betel leaves ethanolic extract are cytotoxic and have potential anticancer properties.