Objective: The study was conducted to determine in vitro antifungal activity of flavonoids extracted from leaves and barks from Rhamnus alaternus L. (Rhamnaceae) against two fungal strains appertaining to two different classes viz. yeast fungi (Aspergillus niger ATCC 16404) and filamentous fungi (Candida albicans ATCC 10231). Methods: Five flavonoid extracts were obtained from leaves and barks of Rhamnus alaternus L. in the mountain of Tessala. Preliminary phytochemical screening was performed by tube staining tests. The inhibition diameters were measured by the solid-state diffusion method. The minimum inhibitory concentrations were determined by the solid dilution method. Results: The minimum inhibitory concentration (MIC) varied according to the flavonoid extract, the vegetative organ and the strain fungal type. The diameters of inhibition range from 5 to 24,2 mm for flavonoid bark extracts and from 7,2 to 17 mm for leaf extracts. On the other hand, these fungal strains were almost resistant to the antifungal marketed drugs viz. (Amphotericin B, Fluconazol, Terbinafine and Econazol Nitrate). The minimum inhibitory concentrations (MIC) obtained range between 25 – 50 µg/mL for Candida albicans strain and 6,25 µg/mL for Aspergillus niger.  The phytochemical screening revealed the existence of certain classes of flavonoid such as flavans and flavonols that may be responsible for this antifungal power. Conclusion: The antifungal power of flavonoids extracted from leaves and barks of Rhamnus alaternus L. varied according to the type of flavonoid extract, its concentrations and resistance or sensitivity of the fungal strains. This plant offers a remarkable therapeutic potential, which reveals its worth in the field of pharmacological industry.