A total of 104 yeast isolates from various natural habitat mainly rotten fruit rinds, forest leaf litter, compost, fruit samples, food stuff and over matured paragrass were isolated on the basis of zone of hydrolysis of cellulose and release of reducing sugars. Among these 31 cellulolytic yeasts were screened.  Five efficient strains (CY-52, CY-58, CY-59, CY-62 and CY-81) were selected from total of 104 isolates, isolated from various natural habitats (mainly rotten fruits, vegetables, sugarcane molasses) on the basis of zone of hydrolysis and release of maximum reducing sugars. The efficient yeast strains were subjected on two delignified substrates i.e., paddy straw and sugarcane bagasse. The yeast isolate CY-59 showed the maximum bioethanol production of 48.18 mg g-1 and 60.51 mg g-1 from paddy straw and sugarcane bagasse, respectively which was on par to reference strain NCIM-3200 and commercial cellulase.