Salinity is one of the most important environmental constraints to the yield of crop plants in nearly 30% of the total land under cultivation and a half of the world's irrigated agricultural land. Salinity, in addition to growth, affects the plant's physiological functions due to the effects of toxic ions and dehydration caused by decreasing the osmotic potential of the soil solution. Saline and alkaline soils are expanding rapidly, especially in arid and semi-arid regions of the country; nearly 15.5 percent of agricultural land in Iran is already affected by salinity. Alternative stress-resilient crops are urgently needed in the face of an ever-increasing threat of land salinization. Therefore, in order to investigate the effects of salinity on physiological, morphological and yield attributes of fennel ( Foeniculum vulgare Mill.), a 3-replicate factorial randomized complete block design pot experiment was carried out in the greenhouse of the College of Agriculture, Isfahan University of Technology, Isfahan, Iran in 2018. Six genotypes of fennel including Kashan, Yazd, Isfahan, Kerman, Shiraz, and Urmia and five levels of irrigation water salinity including 0, 30, 60, 90, and 120 mM NaCl were considered as experimental factors. Leaf chlorophyll, proline and total soluble carbohydrates (TSC) concentrations, leaf water potential (? w ), relative water content (RWC), leaf area, activity of catalase (CAT), superoxide dismutase (SOD) and ascorbate peroxidase (APX), lipid peroxidation and hydrogen peroxide (H 2 O 2 ) concentration were measured in the fifth week after application of salinity stress and plant height, shoot dry mass, seed yield and its components, and Na + and K + concentrations were measured at 12 to 14 weeks after implementing salinity stress. Salinity led to increases in mean proline concentration, chlrophyll a/b, APX activity, and decreases in the mean ? w , chloropgyll a, b and total chlorophyll and caroteoids concentrations and plant height of examined fennel genotypes. Salinity affacted RWC, leaf area, TSC concentration, SOD and CAT activities, H 2 O 2 concentration, umbels/plant, seeds/umbel, individual seed weight, seed weight/plant, plant dry mass, harvest index, Na + and K + concentrations and Na + /K + in a genotype-specific manner. The greatest RWC of the salt-stricken plants was found in genotypes Urmia and Kashan and that of the TSC was detected in Kashan and Isfahan. The greatest leaf area and harvest indicex for the stressed plants was belonged to genotype Isfahan. The greatest individual seed weight, seed weight/plant and plant shoot dry mass for the salt-exposed plants were detected with genotype Urmia. The greatest umbels/plant and seeds/umbel and SOD and CAT activities of the salt-stricken plants were observed in genotype Kashan. While the greatest K + concentration of the stressed plants was found in genotypes Urmia and Isfahan, the smallest Na + concentration and Na + /K + were detected in Kashan and Isfahan. The smallest lipid peroxidation of the stressed plants was found in genotype Kashan but that of the H 2 O 2 concentration was observed in genotypes Shiraz and Isfahan. Salt-induced modifications in a wide range of physiological, growth and yield attributes, taken together, lead us to conclude that fennel is partialy tolerant to sality, as modest salinities in the range of 30 to 60 mM NaCl may be endured with minmal seed and dry mass penalties by genotypes such as Urmia, Kashan and Isfahan. Keywords : Fennel, salinity, antioxidative activity, proline, yield components, plant dry mass