The probiotic properties of four lactic acid bacteria (LAB) strains, Lacticaseibacillus paracasei OR1 and PP1 and Lacticaseibacillus rhamnosus MA3 and PP3, were evaluated. OR1 showed the highest levels of self-aggregation (61.27%) and coaggregation (17.70%) with Staphylococcus aureus. Compared to the crude cell-free supernatant (CFS) and ethyl acetate extract fraction, the water extract fraction of the CFS showed greater antimicrobial activity against Escherichia coli and Bacillus cereus. All LAB strains exhibited the highest levels of total carotenoids, phenolics, flavonoids and antioxidant activity in the CFS, suggesting that they can release water-soluble bioactive compounds into the growth medium. The phytochemical profile of Mahachanok mango, which is rich in bioactive compounds, was improved through LAB fermentation. LC–MS/MS analysis revealed 60 compounds, including phenolic acids (1.11-fold), organic acids (1.21-fold), and amino acid derivatives (1.28-fold), that were more abundant in the fermented Mahachanok mango pulp (FMP) samples than in the fresh samples. Interestingly, the antioxidant proline level increased 377.28-fold, and novel dipeptides and tripeptides were present in the FMP fermented with L. paracasei OR1. Mango pulp is a potential source of nutrients for LAB growth and metabolism; thus, LAB fermentation could be used to produce a functional food product rich in antioxidants and bioactive peptides.