The aim of this Study was to establish a comparative investigation of Antipyretic activity of ethanolic extract of leaves and fruits of the Prosopis cineraria and phytochemical evaluation of ethanolic extracts of these parts. Crude ethanolic plant extracts of leaves and fruits of Prosopis cineraria at a dose of 200 and 300 mg/kg of body weight were used to evaluate the antipyretic activity. These extracts were evaluated by inducing brewer’s-yeast induced pyrexia in albino rats. Results were presented as Mean ± SEM by using SPSS 12.0. Leaves and fruit extracts of Prosopis cineraria decreases hyperpyrexia to a significant level when these results were compared to standard control. The leaves extract shows significant effects in lowering the rectal temperature of rats than fruits extract at 200mg/kg while at dose of 300 mg/kg both leaves and fruit extract reduce pyrexia significantly. The phytochemical evaluation shows that both parts of plant contain saponins, tannins, pholobatannins, flavanoids, alkaloids, steroids and cardiac glycosides. Results indicate that ethanolic leaves and fruit extract of Prosopis cineraria possess significant antipyretic activity at different doses which establishes scientific basis for its traditional uses i.e. in rheumatism. Keywords: Prosopis cineraria, Pyrexia, Paracetamol, brewer’s-yeast, albino rat