Fusarium wilt, caused by Fusarium oxysporum, is a destructive vascular disease of Irish potatoes (Solanum tuberosum L.), leading to substantial yield losses. Management is challenging due to the pathogen’s persistence in soil and the lack of resistant cultivars, while synthetic fungicides pose environmental and health risks. This study evaluated the in vitro antifungal activity of leaf, root, and stem bark extracts from three medicinal plants: Euclea divinorum, Prunus africana, and Carissa edulis against F. oxysporum. Extracts were prepared using solvents of varying polarity: acetone, methanol, and hexane. Antifungal activity was assessed using the poisoned food technique, measuring mycelial growth inhibition. Results demonstrated that solvent polarity and plant organ significantly influenced efficacy. Acetone and methanol extracts exhibited the strongest activity. Complete mycelial growth inhibition (0 mm growth) was achieved with P. africana stem bark (acetone and methanol), C. edulis root (acetone and methanol), and E. divinorum leaf (acetone only). In contrast, hexane extracts showed only moderate activity, with the highest inhibition (57%) from C. edulis leaf. These findings highlight the importance of solvent selection and organ-specific phytochemical profiles in optimizing antifungal activity. The most effective combinations provide a scientific basis for developing botanical fungicides as sustainable alternatives for managing Fusarium wilt in potato production. Further research is recommended to identify active compounds and validate efficacy under in planta conditions.