The diversity of yeast species on grape berries changes depending on various factors. Determination of indigenous yeast intensity and diversity on grape berries is important for increasing the sensory characteristics of wine as well as fermentation efficiency. The natural yeast biota of grape berries affects wine flavour and quality by producing some secondary metabolites and hydrolytic enzymes. Despite the application of different nonconventional yeasts in food and fermentation industries, many significant researches are conducted in finding and improving the new strains having industrially important enzyme activities. Invertase enzyme has a vital role in the food industry in which it increases the sweetness of food without crystallizing them. Here, we studied yeast diversity in grape berries from selected localities and also their invertase activity. We collected grape berries from Alphonse, Kmali Yapmcak, Cavus Efes Karasi, Cinsaut, Atasansi and Isabella grape varieties cultivated in Bozcaada island and Gelibolu peninsula. Twenty-one yeast species belonging to seven genera were identified. The yeast strains having high invertase activities were identified with 5.8S-ITS rDNA sequencing technique. The diversity of yeast biota on berries collected from Gelibolu was greater than that of Bozcaada. Metschnilcowia pulcherrima, Cryptococcus laurentii and Rhodotorula glutinis yeast species were dominant yeast species on grape berries. A total of 294 sucrose grown yeast strains showed growth on sucrose, and 19 of them exhibit the highest invertase activity that is not glucose repressible. These 19 yeast strains were identified as Starmerella bacillaris using 5.8S ITS rDNA region and the phylogenetic analysis was inferred with the Maximum Parsimony method.