Humans have altered the forests of urban regions drastically, thereby reducing the original forests to isolated fragments. Such fragments may contain remnants of the original vegetation. Nanmangalam Reserve Forest (NRF), located in the Metropolitan Chennai, Tamil Nadu, India, is an example of such a forest fragment, covering an area of 321 ha. A total of 449 angiosperm species belonging to 313 genera representing 83 families were recorded from NRF. Amongst the species, 79% were dicots and 21% were monocots. The most genera/species rich families were Fabaceae (37/69) and Poaceae (34/52). The species rich genera included Cassia (10), Crotalaria (7), Erogrostis, Hedyotis and Phyllanthus (6 each). Six endemic species were recorded. This diversity amidst a rapidly expanding city has to be protected in order to enable the conservation agenda of urban areas.