An experiment was conducted during Kharif, 2018 to evaluate the mean performance and to find out the nature and extent of genetic variability among eight inbreds of parthenocarpic gynoecious cucumber genotypes under naturally ventilated polyhouse situated at polyhouse complex of department of Horticulture (Vegetable and Floriculture), BAU, Sabour, Bhagalpur, Bihar of Eastern India. The experiment was laid out in randomized block design with three replications. Data were taken on six competitive plants for 13 growth and yield attributing traits, including total soluble solids (TSS) and per cent disease index for downy mildew (PDI). Among eight cucumber inbreds, BRPCU-1 showed earliness in respect of days to first female flower, node to first female flower and days to first fruit harvest, and disease tolerance to downy mildew. However, inbreds BRPCU-3, BRPCU-5 and BRPCU-7 were high yielders in fruits per plant and yield per plant. Non-additive gene effects were manifested for most of the earliness, while additive gene effect was observed for yield and fruits per plant.