Two field experiments were carried out during 2014/2015 and 2015/2016 seasons to evaluate the effect of different levels of magnesium sulphate (0, 25, 50 and 75 kg/feddan) on growth, yield, chemical composition, essential oils and their constituents of three curly parsley cultivars (Petra, Krausa and Bravour) under South Sinai conditions (Ras Sudr). Results showed that Krausa cultivar surpassed the two others cultivars in stem/leaves per plant, plant fresh weights per square meter, plant fresh yield per feddan, chlorophyll a, carotenoids, nitrogen, magnesium contents and fractions for essential oils responsible on the preferred parsley aroma. On the other hand, Petra cultivar showed the superiority in plant dry weight, chlorophyll b, total chlorophyll, phosphorus, potassium content, essential oil and total oil yield. Magnesium sulphate at 75 kg/feddan resulted in the best values of the studied characters. The highest growth and yield values were obtained with Krausa cultivar and 75 kg magnesium sulphate per treatment, while, the Petra cultivar with 75 kg per feddan gave the highest content of essential oil under salt stress.