The use of medicinal plants in a variety of health conditions remains essential for the discovery of new treatments. The present study aimed to investigate the bioactive properties of three native plants from Cabo Verde Islands, namely Artemisia gorgonum Webb, Sideroxylon marginatum (Decne. ex Webb) Cout., and Tamarix senegalensis DC., contributing to the characterization of less-known medicinal plants and their potential benefits for human health. Known compounds, such as kaempferol, quercetin, caffeyolquinic, and apigenin derivatives, among others, were detected in the plant species under study. Overall, all species demonstrated good antioxidant capacity, especially the ethanolic extracts of A. gorgonum (EC50 = 0.149 mg/mL) in TBARS assay. Moreover, the ethanolic extracts of the studied plants showed cytotoxic properties against tumor cells, and again the A. gorgonum extract proved to be the most effective in inhibiting tumor growth, mainly in the CaCO2 (GI50 = 17.3 μg/mL) and AGS (GI50 = 18.2 μg/mL) cell lines. Only the ethanolic extracts of T. senegalensis and S. marginatum demonstrated anti-inflammatory activity, albeit weak (EC50 = 35 and 43 μg/mL, respectively). The present study contributed to increased knowledge about the bioactive properties of these plants commonly used in traditional medicine, some of which was discussed for the first time, opening new perspectives for their use in a wider range of health conditions, especially in African countries, where access to modern health care is more limited.