In order to investigate the effects of osmotic stress on forage sorghum varieties at critical stage of germination to salinity stress. A study was conducted at the Seed Technology Laboratory of Mansoura University, Egypt during April to June 2012. Three forage sorghum cultivars (Mabrouk, Horas, Pionner-8581) were evaluated in the salinity concentrations of 0, 2, 4, 6, 8, 10, 12, 14 and 16 dSm-1 NaCl. Four parameters namely final germination percentage, germination index, energy of germination and seedling vigour index were estimated. Eight seedling characters namely shoot and root length, shoot and root foliage weight, shoot and root dry weight, seedling height reduction and relative seedling dry weight were measured. Forage sorghum cultivars significantly varied in means of final germination percentage, germination index, seedling vigor index, energy of germination, shoot and root lengths, shoot and root fresh weights, shoot and root dry weights, seedling height reduction and relative dry weight. Horas cultivar surpassed other cultivars in all of the studied characters followed by Mabrouk cultivar which came in the second rank, while Pioneer 858 cultivar came in the last rank. Pioneer 858 cultivar recorded highest values of seedling height reduction and relative dry weight followed by Mabrouk cultivar, while, Horas cultivar came in the last rank for both characters. Increasing salinity levels from 0 to 15 dSm-1significantly decreased germination percentage, germination index, seedling vigor index, energy of germination, shoot and root lengths, shoot and root fresh weights, shoot and root dry weights and relative dry weight, the control treatment recorded the highest averages of these characters. Thus, the lowest averages of these characters were recorded with highest salinity levels i.e. 15 dSm-1 . Seedling height reduction percentage was increased significantly with increasing salinity levels from 0 to 15 dSm-1 . Results clearly showed that germination index, seedling vigor index, shoot and root lengths, shoot and root fresh weights, shoot and root dry weights, seedling height reduction and relative dry weight significantly affected by the interaction between forage sorghum cultivars and salinity concentrations. It could be concluded that Hoars cultivar was more tolerant to salinity stress followed by Mabrouk cultivars which must be put in breeding program of forage sorghum under salinity conditions.