An experiment was conducted to investigate effects of supplemented L-carnitine, ascorbic acid and probiotics on productive performance, carcass characteristics and some bacterial and histological aspects in locally-developed broiler strain. 252 unsexed chicks 2 weeks of age were reared up to 8 weeks of age were distributed into 7 treatments in 6 replicates of 6 birds each. The experimental groups were as follows: T1: Control group fed basal diet. T2: Basal diet supplemented with 500 mg ascorbic acid / Kg diet. T3: Basal diet supplemented with 1000 mg ascorbic acid / Kg diet. T4: Basal diet supplemented with 75 mg L-carnitine / Kg diet. T5: Basal diet supplemented with 150 mg L-carnitine / Kg diet. T6: Basal diet supplemented with 0.5 g Probiotic / Kg diet. T7: Basal diet supplemented with 1.0 g Probiotic / Kg diet. The results showed that live body weight, daily weight gain, daily feed consumption or feed conversion ratio were insignificantly different during the first 2 weeks of studied period among all groups. Birds fed T2 diet gained significantly higher weight compared with other groups at overall period. While feed conversion ratio of birds fed T4, T5, T6 and T7 were the best significantly compared with the other groups. Dressing percentage of all tested groups was increased significantly compared with control group. While birds fed T3 or T5 diets deposited significantly less abdominal fat compared with the other groups. Microbial studies showed that aerobic bacteria decreased by feeding different treatments in caecum and small intestine compared with control. Also, anaerobic (beneficial) bacteria increased in caecum and small intestine in comparison with control. As well, feeding birds on probiotics or ascorbic acid had completely eliminated Campylobacter from chicken meat. Probiotics treatment was the more effective in decreasing total bacterial count in carcass meat. Histological observation revealed that dietary treatments had a positive effect on the number and size of fasciculi and consequently their myofibers of muscles, normal liver and spleen structure was noticed, expect for some slight changes. Therefore, it is suggested that L-carnitine, ascorbic acid or probiotics, could be used safely as feed additives to improve performance without any adverse effect on body organs or gastro-intestinal tract microbial population.