Chemical compositions (fatty acids, total phenolic compounds, flavonoids) and the in-vitro biological activities (antioxidant and antimicrobial activity; and growth induction of edible fungal strains) were compared for four varieties of mango seeds. Hexanic extract (HE) showed a fatty acid profile with a higher proportion of oleic acid. In the ethanolic extract were found variable total phenolic contents (103 to 125 mg GAE/g dry weight) and flavonoid contents (0.72 to 0.8 mg QE/g dry weight). This study reports for the first time the presence of procyanidin B1 in ethanolic extracts. The antioxidant activity showed IC50 values ranging from 3.09 to 3.42 μg/mL for ABTS•+ and 12.17 to 13.93 μg/mL for DPPH•. The ethanolic extract from the seed of the Yulima variety showed the highest percentages of inhibition against Staphylococcus aureus. Residues removed from ethanolic extraction of the seed kernel (EKR) induced the growth of edible fungal strains: Lentinus crinitus and Pleurotus tubarius. The data obtained show the potential of the seeds from these mango varieties, which could lead to alternative uses in various industry sectors and the use of this agricultural byproduct.