Pyrexia or fever is a disease caused as a result of secondary impact of other diseased states due to the resetting of the hypothalamic set-point. From scientific discovery, antipyretic drugs such as asipirin, NSAIDs, opiods have been developed for use and of which mostly produces side effects including gastrointestinal bleeding ,renal,hepatic effect,etc(Cheng et al.,2005,Sharma et al., 2010).Therefore, many herbal plants have been found to be having antipyretic effects.Ocimum gratissimum is a shrub commonly found in Africa and has been used to treat bacterial fevers locally. This study investigates the antipyretic activity of the methanolic extract of Ocimum gratissimumon brewer’s yeast induced fever in experimental rats.30 albino rats weighing 150g-200g were used. They were divided in to six groups of five rats each. Group one serve as control(n=5) and was given 1ml of normal saline,group two (n=5)was treated with brewer yeast alone, group three(n=5) was given 100mg/kg of asipirin, while groups four,five and five were treated with 300mg/kg,200mg/kg and 100mg/kg (n=5)of Ocimum gratissimum respectively. A suspension of brewer’s yeast was injected subcutaneously to induce fever in all the experimental animals. After 18hrs, the rectal temperature was taken and the animals were administered Ocimum gratissimum(100mg/kg.200mg/kg,300mg/kg) and aspirin (standard group,100mg/kg) orally. The body temperature of the rats was measured rectally over a period of 4hours.Ocimum gratissimum(100mg/kg, 200mg/kg and 300mg/kg) significantly reduced yeast induced pyrexia ,36.88±0.39°C, 36.43±0.26°C and 35.83±0.46°C when compared the group two(20ml/kg, brewer’s yeast) temperature of 37.80±0.18°C(*p<0.05,respectively). The group three(asipirin,100mg/kg) also show significant reduction 36.55±0.22°C,*p<0.05,compared with group two(20ml/kg ,brewer yeast) with temperature 37.80±0.18°C.Thus, this experiment shows that the antipyretic effect of ocimum gratssimum is dose dependent and the effect is as a result of the flavonoid component of the extract.These data therefore suggest that methanolic extract of Ocimum gratissimum leaves possesses significant antipyretic activity and it mechanism could be by inhibition of/release inflammatory mediators. Keywords:Ocimum gratissimum, brewer’s yeast, antipyretics, asipirin,temperature