Anticoccidial efficacy of the herbal mixture of Vernonia amygdalina (VA 10%) and Azadirachta indica (AI 10%) was tested against naturally infected broiler coccidiosis. A total of 100 four week old broilers naturally infected with coccidiosis were divided into five treatment groups based on the number of coccidian oocyst they contained. Group I which contained 20,700 oocyst counts served as a negative control. Group II contained 20,000 oocyst counts served as a positive control and was treated with a synthetic drug, amprolium, at recommended dose of 0.6 g/L for seven days. Groups III and IV with 20,200 and 20,500 oocyst counts were treated with 10% of V. amygdalina and 10% A. indica, respectively. Group V contained 20,400 oocyst count and was treated with the mixture of 10% each of V. amygdalina and A. indica. Groups II, III, IV and V were treated continuously for seven days. Oocysts were identified using the sodium chloride floatation method. The number of oocysts egg per gram (EPG) of faeces was determined by modified McMaster counting technique. Oocysts EPG decreased steadily in all the treated groups with a marked reduction in groups II and V. The packed cell volume (PCV), red blood cell (RBC) and white blood cell (WBC) count were determined using standard haematological methods. PVC, haemoglobin (Hb) and RBC count of the treated birds were significantly (p< 0.05) higher than those of the infected untreated groups. Hematological parameters and histological features showed a significant increase in WBC, RBC and lymphocytic infiltration; indicative of cell mediated immune response. Lower heterophil/lymphocytic ratio of the groups III, IV and V after treatment suggested immunomudulatory effect of the herbs (V. amygdalina and A. indica). Hence, the plants are capable of boosting the immunity of birds with either clinical or sub-clinical coccidia infection following subsequent exposure.