Seaweeds are the natural marine algae which have several properties to act as natural preservatives to extend the shelf life of perishable foods without affecting their quality and causing side effects. Locally available and cheap fruits such as tomato are perishable very easily due to its high water content. Seaweed gel coating is a good choice, easily available and cheap natural preservative abundantly available in the Indian coasts. The present study was undertaken to extend the shelf life of the tomatoes using seaweed gel coating at different concentrations. Two seaweeds namely Kappaphycus alvarezii (red algae) and Sargassum tenerrimum (brown algae) was selected due to their high gelling property. Selected seaweeds were collected in dry form from Aqua Agri Processing Limited, Mana Madurai (SIPCOT) Tamil Nadu, India. The seaweed extracts were tested for phytonutrients, antibacterial and anti-fungal activity using standard procedures. The shelf life of seaweed coated tomatoes using different concentrations of the seaweed extract (gel) was tested. From the results, it is understood that the phytonutrients namely flavonoids, steroids, saponins and tannins are present in both the selected seaweeds. Antibacterial and antifungal activity of Kappaphycus alvarezii showed higher inhibition zone than S. tenerrimum against common pathogens. Quality characteristics and shelf life evaluation was based on water loss, texture, ascorbic acid content, juice content, total soluble solids (TSS), total acidity and TSS/total acidity ratio, respectively. The results pointed out that K. alvarezii was the most effective in maintaining the quality characteristics of tomato fruits and it also supports the fruit quality during storage period than S. tenerrimum. Thus, from the results of the study it is concluded that the better quality characteristics and shelf life of tomatoes can be increased by coating seaweed gel and it can be used as a bio preservative in fruit and vegetable preservation.