Antioxidants are increasingly being recommended because they act directly on oxidative processes and may prevent diseases and problems associated with disease control and aging. Therefore, there is a constant search for antioxidants from natural sources for the isolation of antioxidant biomolecules. Seaweeds are an excellent source of natural antioxidant bioactive compounds which can be used as dietary supplements or as antioxidants in controlling bacterial infection in aquaculture farms as well as in the food industry. A great deal of effort has therefore focused on using available techniques to identify natural antioxidants from seaweeds. The aim of the present study was to analyse the bioactive compounds extracted from ethanol extract of the seaweed Chaetomorpha antennina by GC-MS study and to evaluate its antioxidant and antibacterial activities for controlling bacterial infection in shrimp pathogens through immersion and intramuscular infection study. The antioxidant activity of the selected seaweed was estimated in order to evaluate the efficiency of its ethanol extract since this will help in finding novel bioactive compounds with antioxidant & radical scavenging properties, which in turn can reveal the unexploited properties of this seaweed which could be used in the food and pharmaceutical industry. © 2014 Elsevier B.V.