A field research study was conducted at the experimental station of the Faculty of Agriculture, Alexandria University during 2017/2018 and 2018/2019 seasons to investigate the effect of three sowing dates (1, 15 and 30 November) and three phosphorus fertilizer rates (zero, 36 and 72 kg P2O5/ha.) on straw and seed yields and their components beside seed oil content of Sakha 5 flax cultivar. The obtained results showed significant effects for both sowing dates and phosphorus fertilizer rates, with significant interaction between them on seed index and number of seeds/ capsules in the second season (2018/2019) and seed weight/ plant in the two seasons. The first and second sowing dates were not significantly different from each other in straw yield/ha, but they significantly dominated over the yield of the third sowing date in both seasons. Straw yield/ha ranged from 7.45 to 8.16 t/ha in the first season and from 7.90 to 8.38 t/ha in the second season. The sowing date of 15th Nov. significantly increased number of capsules/plant and seed yield/ha more than the other two sowing dates. The highest seed yields/ha were 2.55 and 2.50 t/ha under 15th Nov. sowing date in the two seasons, respectively, followed by 30th Nov. date. Application of 36 kg P2O5/ha produced the highest means of straw yield and straw yield components but no significant differences were found between the 36 and 72 kg P2O5 /ha for these traits. The highest means of seed yield and seed yield components were detected under the 36 kg P2O5/ha rate with significant differences from the highest phosphorus fertilizer rate or zero phosphorus fertilizer. The highest oil percentages were 46.51% and 46.68% under the 36 kg P2O5/ha rate in the two seasons, respectively, followed by the highest rate while the lowest oil percentages were 45.09 % and 45.08% under zero phosphorus fertilizer in the two seasons, respectively. Regarding the significant interaction effect, the obtained results indicated that 30th Nov. with 36 kg P2O5 /ha gave higher values of seed index and number of seeds/ capsules in the second season, seed weight/ plant increased with both 15th or 30th Nov. under 36 kg P2O5 /ha in the first season, whereas in the second season the highest value was obtained for 15th Nov. under 36 kg P2O5 /ha.