The changes in polyphenols and caffeine alkaloid compositions of black tea, due to the variations of fermentation temperature were investigated. Black tea was manufactured by fermentation at various temperatures such as 26oC (Control) 30o, 36o and 40o where the tea leaves were fermented initially for 45-50 minutes at an private factory. During this oxidation process, withered and rolled leaf looses its green colour acquiring copper red to brown colour. Drying terminates these biochemical changes and remove moisture thereby the colour of fermented leaves turns from copper red to black and fermentation is arrested. Total polyphenols content were determined colorimetrically using Folin-Ciocalteau method and caffeine was isolated from all the samples by Liquid-Liquid extraction using chloroform. The results showed that increase in fermentation temperature significantly increases caffeine content whereas polyphenols content showed a great reduction at 30o, 36o and 40o. However further studies are needed to evaluate the organoleptic characters such as taste and aroma.