Two field trials were conducted during two successive summer seasons of 2008 and 2009 at the Experimental Farm, El Kassasein Research Station, Ismailia Governorate, to elucidate the effect of foliar spray with seaweed extracts (without, 1g/ l and 2g/ l) and four tomato hybrids (Master R.S., K615, K111 and K 306) as well as their interaction on growth, dry weight, flowering, fruit setting, physical characters, yield and chemical constituents of tomato plants (Lycopersicon esculentum Mill.) during summer season under sandy soil conditions. Tomato hybrid K615 recorded the highest values of leaf area, number of leaves/plant, leaves and total dry weight, and fruit diameter, while the hybrid K306 gave the highest values of plant height, setting percentage, fruit length, number of fruits/plant, yield /plant and total yield /fed. As well as K% content in fruits.                                                                                                                        Spraying tomato hybrids with seaweed extracts at a rate of 1g/ l recorded maximum values of plant growth characters, leaves and total dry weight, while spraying the plants with seaweed at 1 or 2g/ l reflected the highest values of setting percentage, number of fruits/plant, yield/plant and total yield /fed. as well as total soluble solids as compared to the control. The interaction treatment between the hybrid K615 and foliar spray with seaweed extracts at 2g/ l gave the highest values of leaves number/plant, number of shoots/plant, leaf area, dry weight, fruit diameter, number of fruits/plant, N% and protein % as well as total soluble solids. On the other side, the combination between tomato hybrid K306 and foliar spray with seaweed extracts at 2g/ l gave the best values of plant height, number of shoots/plant, setting percentage, fruit length, yield/plant and total yield /fed. as well as K% content in fruits.