In an attempt to find potential functional foods in Tanzania, a study was conducted to assess bioactivity of 18 ethyl acetate extracts from nine (9) Ascomycetes strains. Namely; Candida tropicalis, C. pararugosa, Clavispora lusitaniae, Issatchenkia orientalis, Pichia kudriavzevii, Pichia guilliermondii, Galactomyces geotricum, Debaryomyces hansenii and Yarrowia lipolytica isolated from traditional fermented milk “mtindi”. Lethality test of the extracts was determined using Artemia salina naupalii in a Brine Shrimp Test (BST). The lethal concentration (LC50) obtained ranged from 89.7µg/ml to over 1000 µg/ml. Bioactivity results showed that, one of the 18 extracts had exhibited a strong antibacterial activity against Staphylococcus aureus, Pseudomonas aureginosa and Vibrio cholera having minimum inhibitory concentration (MIC) values of 0.1653mg/ml on each account. More than 40% of extracts exhibited strong to moderate antifungal activity against Cryptococcus neoformans (MIC 0.16 mg/ml – 1.25 mg/ml). In conclusion, these results suggest that yeasts found in traditional fermented milk have potential biological activity that could be used for treatment of some diarrhoeal and fungal infections and possibly tuberculosis.