The present study was carried out at Nuclear Research Center, Atomic Energy Authority, Inshas, Sharkia Governorate, Egypt, during the two consecutive seasons of 2013/2014 and 2014/2015 to study the effect of using different gamma irradiation doses, potassium fertilization levels and their interaction treatments on gridgeth, yield components, fixed oil percentage and leaf green color degree (SPAD-unit) of borage (Borago officinalis, L.) plant. The used gamma irradiation treatments were 0 (control), 2, 4, 6, 8 and 10 kilo rad (kr). Whereas, potassium fertilization levels were 0 (without K addition), 50 and 100 kg potassium sulphate/faddan, each treatment of gamma irradiation doses was combined with each level of potassium fertilization to form 18 interaction treatments. The obtained results cleared that using gamma irradiation dose of 2 kr increased most values of plant height, dry weight of herb per plant, number of inflorescences per plant, seed yield per plant and per faddan, fixed oil percentage and leaf green color degree. Furthermore, the maximum increase in this respect was obtained from the potassium fertilization treatment of 100 kg potassium sulphate/faddan compared with the other ones under study. Generally, the interaction treatment between 2 kr of gamma irradiation with 100 kg potassium sulphate/faddan of potassium fertilization mostly gave the maximum increase in the above mentioned parameters. Therefore, it seems to be recommended treatment under Sharkia Governorate conditions. Moreover, potassium fertilization at 100 kg potassium sulphate/faddan could be overcome the harmful effect of gamma irradiation in this respect on borage plant.