Two field trials were performed during 2020/2021 and 2021/2022 seasons at Sakha Agricultural Research Station to determine the optimum levels of mineral fertilizer (Nitrogen) and bio-fertilizers (Azotobacter and Azospirillum) for yield and yield attributes for new flax cultivars (Sakha 5 and Sakha 6). Split-plot design with four replicates was the experimental design. The main-plots were selected for ten mineral and bio-fertilizers treatments and the sub-plots were chosen for two flax cultivars. The results referred that using 100% of the recommended dose of nitrogen (RDN) or 75% RDN + Azotobacter + Azospirillum treatments significantly achieved the highest values for technical length, stem diameter, straw yield/plant and per feddan, fruiting zone length, number of capsules/plant, seed yield per plant and also per feddan, oil content %, oil yield/fed, also fiber length, fiber % and fiber yield/fed through each season. Sakha 6 cultivar significantly outperformed Sakha 5 in technical length, stem diameter, straw yield/plant and per feddan, seed index, seed yield/plant, fiber length, fiber % and fiber yield/fed, while Sakha 5 was superior in number of capsules/plant, oil content % and oil yield/fed in the first and second seasons. It can be concluded that the most economic return for farmers was gained from using the combination of 75% of the recommended dose of nitrogen + Azotobacter + Azospirillum bacteria with Sakha 6 cultivar for the best straw and fiber yield per fed or with Sakha 5 cultivar for the best oil yield per fed under the environmental conditions of North Delta of Egypt.