Cancer is a serious disease that spread all over the world, despite the great production of different treatments. Whereas the treatments have harmful side effects, toxic, high cost and often unsuccessful. For that reasons, the researchers started to seek an alternative treatment like natural products derived from plants. Saudi Arabia is characterized by its rich biodiversity because it possesses different environmental conditions. Whereas the southwest region is famous by its classified and unclassified medicinal plants. Unfortunately, plants of that area have not been studied extensively. The current study aims to explore the potential anticancer effects of Kanahia laniflora and Kleinia pendula extracts against human lung cancer cells A549, breast cancer cells MCF-7, liver cancer cells HEPG-2, colon cancer cells HCT-116, and prostate cancer cells PC-3. To achieve the goal of this study, collected plants from Faifa mountains and Wadi Ayaa (southwestern Saudi Arabia) were classified, dried, and then grinded. To extract chemical contents of Kanahia laniflora and Kleinia pendula, each plant was divided into three groups, the first was soaked in distilled water, the second was soaked in ethanolic alcohol and the third was soaked in methanolic alcohol.