The differential anti-proliferation effect of white (Pueraria mirifica), red (Butea superba) and black (Mucuna collettii) Kwao Krua plant extracts on the growth of MCF-7 cells was evaluated after 4 days of incubation. The percent cell growth comparison was based on protein determination of the harvested cells in parallel with the control group and Pueraria lobata treatment group. Pueraria lobata led to no proliferation and a mild anti-proliferation effect on the growth of MCF-7 cells. Pueraria mirifica caused proliferation at 1 microg/mL and an anti-proliferative effect on the growth of MCF-7 cells at 100 and 1000 microg/mL with an ED50 value of 642.83 microg/mL. Butea superba led to no proliferation and an anti-proliferation effect on the growth of MCF-7 cells at 10, 100 and 1000 microg/mL with an ED50 value of 370.91 microg/mL. Mucuna collettii led to no proliferation and an anti-proliferation effect on the growth of MCF-7 cells at 100 and 1000 microg/mL with an ED50 value of 85.36 microg/mL. The results demonstrated that only Pueraria mirifica showed an estrogenic effect on MCF-7 cell growth and a clear antagonistic effect with E2 at high concentration. Butea superba and Mucuna collettii exhibited only anti-proliferation effects on the growth of MCF-7 cells in relation with a possible anti-estrogen mechanism or a potent cytotoxic effect.