The hidromethanolic (Met/W), ethyl acetate (EA((EA/W))), and water (W-(EA/W)) extracts from Teucrium sandrasicum leaves (L) and flowers (F) were investigated for antioxidant properties and antiproliferative effects on HeLa, MCF-7, and L929. The highest DPPH scavenging, metal chelating capacities, and total phenolic and flavonoid contents were observed in Met/W-L. The highest hydroxyl scavenging and reducing power capacities were found in EA((EA/W)L). Met/W-L, EA((EA/W)L) and EA((EA/W)F) inhibited cancer cell growths, while they did not show significant cytotoxicity on L929. While the reactive oxygen species (ROS) levels were generally close to controls in HeLa, they were induced in MCF-7 with the treatment of Met/W-L, EA((EA/W)L), and EA((EA/W)F) and acted as antioxidant for L929. The highest apoptosis inductions were observed in Met/W-L-treated HeLa and EA((EA/W)L)-treated MCF-7, which were supported with the changes in mitochondrial membrane potentials. The highest caspase-9 activities were found in Met/W-L-treated HeLa and EA((EA/W)F)-treated MCF-7. Caspase-3 activity was only induced in EA((EA/W)F)-treated HeLa.