The present investigation was conducted during Zaid seasons 2022- 23 (Y1) and 2023-24 (Y2) to estimate heritability in narrow sense and genetic advance in percent of mean by using Line x Tester mating design at the Main Experiment Station (MES) of the Department of Vegetable Science, Acharya Narendra Deva University of agriculture & Technology, Kumarganj, Ayodhya (U.P.) India. All selected diverse parents of cucumber were crossed in a Line x Tester mating design from generating experimental material. All the ten parents and three testers their 30 F 1 hybrids ware grown in randomized block design with three replications. Observation were recorded for the 18 characters. High heritability coupled with high genetic advance were observed for days to first staminate flower anthesis, days to first pistillate flower anthesis, vine length (m), number of primary branches per plant, number of fruit per plant, fruit yield per plant (kg), ascorbic acid (mg/100g), non- reducing sugar (%) and total sugar (%)in the year over season pooled. High heritability (narrow sense) along with high genetic advance in per cent of mean were observed for most of important economic traits showing ample scope of crop improvement by selection. Moderate heritability coupled with high genetic advance were observed for node number to first staminate flower appearance, node number to first pistillate flower appearance, fruit breadth (cm) and TSS (Brix) shows moderate heritability coupled with high genetic advance.