Two celeriac cultivars (Apium graveolens var rapaceum M.) [CV Brilliant, "BC" and CV Giant Smooth Prague, "GSPC"] were assessed for yield and quality characteristics at the Experimental Farm, Faculty of Agriculture, Al-Azhar University during two successive winter seasons of 2008/2009 and 2009/2010 years. In order to investigate the effect of three harvesting dates "HD1", "HD2" and "HD3" at 120, 135 and 150 days after transplantation respectively on Celeriac "Shoots and swollen root" yield and quality. Physical characteristics of plant length, leaves number per plant, leaf length and swollen root diameter were measured. Pigment content analysis of Chlorophyll a, Chlorophyll b, total Chlorophyll and Carotenoids were also determined. Nutritional composition of Titratable acidity (TA), Ascorbic acid (AA), total soluble solids (TSS), total sugar (TS) and dry weight in leaves and swollen roots of two celeriac cultivars were determined. Yield of leaves and swollen roots weight were also recorded. There were high significant differences among harvesting dates for all studied characters in both growing seasons. As well as high significant differences between two cultivars were detected, for all studied characters in both seasons. HD3 gave the highest value for leaf pigment content, nutritional composition of leaf and swollen root (TA, AA, TSS), total sugar and dry weight in both cultivars in both growing seasons. However, HD3 improved the nutrceutical value, leaf and swollen root yield in cultivar GSPC more than BC in both seasons. The results of this investigation proved that the most suitable consumption of celeriac leaves and/or swollen roots are at the delayed harvesting to 150 days after transplanting "HD3". In general, the interaction between HD3 and GSPC cultivar produced higher values for most investigated characteristics. So that it's recommended under such conditions to grow CV Giant Smooth Prague, "GSPC" and to be harvested after 150 days from transplanting.