The current work aimed to assess the potential of the green seaweed Ulva lactuca (U. lactuca) as an alternative ingredient in broiler chicken diets. The effect of substituting 1.0 or 3.0% of corn with U. lactuca on performance, carcass characteristics and serum constituents of broilers from 12 to 33 d of age was evaluated. Three treatments were distributed in a RCBD design: T1, control diet (0% U. lactuca); T2, 1.0 % U. lactuca; T3, 3.0 % U. lactuca. A total of 45 chicks were assigned to three treatments (5 replicates per treatment) used in this experiment. Cumulative feed intake (FI), body weight gain (BWG), feed conversion ratio (FCR) and nutrients retention from 12 to 33 d of age were not affected by treatment (P>0.05). Birds which had received T3 had a higher dressing percentage and breast muscle yield compared to those which had received T1 or T2. Serum total lipid, cholesterol and uric acid concentrations were significantly lower in birds which had received T2 and T3 (P<0.05). Serum enzymes and electrolytes were not influenced by any dietary treatment except for alanine transaminase (ALT) which was significantly lower for the treated groups. Based on presented evidences, it is recommended to substitute 3.0% of corn with green seaweed (U. lactuca).