A split-split plot field experiment with three replications was carried out at Sakha Agricultural Research Station, Kafre El-Shiekh Governorate, Egypt, during two seasons of 2017/18 and 2018/19 to study the effect of different harvesting dates (after 145, 155 days and 165 days from sowing), sowing rates (60, 70 and 80 kg seeds/fed) on yield and its components of some flax varieties (Giza 11, Giza 12 and Marlin). Harvesting flax plants at either 165 or 155 days from sowing consider as optimum dates to achieve highest estimates for technical length, fruiting zone length, straw yield/plant, number of capsules/plant, seed oil%, seed yield/fed., straw yield/fed and fiber yield/fed. The flax variety Giza 12 ranked first and recorded highest mean values of technical length, fruiting zone length, straw yield/plant, number of capsules/plant, seed oil%, seed yield/fed. and straw yield/fed, in both seasons. Meanwhile, the two newly flax varieties i.e., Giza 12 and Giza 11 did not differ significantly in most studies characters in both seasons. The introduce variety Marline recorded maximum estimates for fiber % and fiber yield /fed. Increase seeding rates up to 70 or 80 kg seeds/fed caused an increment in most studied traits without significance between them concerning most characters. The dual interaction of harvesting dates with flax varieties had significant effect on fruiting zone length, seed index, stem diameter, seed oil%, fiber% and fiber yield/fed.. In addition to, the triple interaction of harvesting dates with flax varieties and seed rates had significant effect on technical length and fiber yield/fed.