The experiment was conducted in the rabbits farm belonging to of Environmental Studies and Research Institute, University of Sadat City, Menoufia Governorate, Egypt. The aim of this study was to study the effect of adding brown algae (Sargassum muticum) and natural antioxidants (Senecio glaucus) in powder or extract form on the growth performance of growing New Zealand white rabbits aged 4 weeks with an average weight of approximately 600 grams. A number of 36 rabbits were used in this experiment, divided randomly into six groups, each group consisting of 6 rabbits. The first group D1 was fed on commercial diet 17% protein (positive control), the second group was fed on a basic diet 14% protein (control negative), the third and fourth groups D3 and D4 were fed on a basic diet supplemented with Sargassum algae in the form of extract and powder and the fifth and sixth groups D5 and D6 were fed Senecio glaucus in the form of extract and powder. The experiment lasted (10) weeks period. The results indicated that the addition of Senecio glaucus powder to the feed of growing rabbits with a level of 10g of Senecio glaucus powder/kg of feed led to a significant increase in the growth performance variables (final body weight, daily weight gain, feed conversion ratio and performance index), while rabbits fed on the D5 diet (Basal diet + 10 ml of Senecio glaucus extract /kg feed) had the lowest feed consumption. Also, there was an improvement in some characteristics of the carcass, blood and microbial activity in the cecum. Also, observed an improvement in the economic efficiency by adding Senecio glaucus and Sargassum algae compared to the control groups.