Phaulopsis falcisepala is an herb found in the forest zone of West Africa. It is applied ethnomedicinally for treating wounds and cancer. This study investigated the chemical constituents, cytotoxicity, and antimitotic activity of P. falcisepala leaves and stems. Chemical constituents were evaluated using phytochemical methods. Cytotoxicity was investigated using brine shrimp lethality and Allium cepa root growth inhibition assays. Antimitotic activity and induction of chromosomal aberrations were assessed by cytological examination of treated A. cepa meristematic cells. Chemical investigation revealed the presence of diverse bioactive chemical groups, including alkaloids, terpenoids, tannins, flavonoids and saponins in various extracts of the leaves and stems of P. falcisepala. Aqueous and methanol extracts contained copious amounts of the phytochemicals while ethyl acetate and n-hexane extracts contained moderate to trace amounts. The extracts demonstrated toxicity against brine shrimps, with LC50 values in the range 13.1–52.2 µg/mL. The extracts significantly inhibited A. cepa root growth, with IC50 values in the range 63.91–87.4 µg/mL and 45.34– 81.15µg/mL for 24 and 48 h treatments. The extracts (IC50 values in the range 46.2–94.23 µg/mL and 30.79–75.81 µg/mL for 24 and 48 h treatments) produced significant antimitotic effect comparable to or greater than that of methotrexate (IC50 value >125 µg/mL). Cytological examinations revealed that the extracts induced mitotic arrest and chromosomal changes. This study reports for the first time the phytoconstituents and cytotoxic activity of P. falcisepala supporting its ethnomedicinal use and could serve as the basis for further pharmacological studies and isolation of bioactive principles.