Ambattur Lake is situated in Ambattur of Thiruvallur District of the state Tamilnadu. It is one of the biggest lake acts as reservoir in Chennai, located in Thirumullaivayil, Tamilnadu. Surface water samples were collected from five different locations at regular interval during October 2010 to March 2011. Physico-chemical parameters and biological parameters were investigated. A total of 22 species of plankton consisting phytoplankton and zooplankton were recorded and fluctuations among physico-chemical parameters during the investigation were also noticed. Centropyxis spinosa, Arcella discoides, Euglypha acanthaphora among protozoa; Lecane curvicornis of rotifer and cyclopoid nauplii were found to be dominant during the study.