This paper presents the assessment of both the natural and planted species diversity of the Sitakunda Botanical Garden and Eco-park, Chattogram. A total of 267 plant species from 101 families are recorded in three zones namely disturbed, undisturbed and planted areas. Among them 153 plant species recorded from the natural undisturbed area belonging to trees (45 species), shrubs (44 species), herbs (34 species) and 30 species of climbers. Fifty two species were documented from disturbed and planted areas. Mikania cordata, Chromolaena odorata, Hyptis suaveolens, Mimosa pudica and Ageratum conyzoides are dominant species in the disturbed zone and Ficus hispida are the most dominant tree species in the undisturbed zone. The highest Importance Value Index (IVI) showed 28.08 for Holarrhena antidysenterica and the lowest 1.05 for Mangifera sylvatica in natural patch. Syzygium fruticosum showed the highest IVI of 27.81 and Pinus caribaea showed the lowest (0.93) IVI in plantation site. Most of the species are regenerating from the root suckers. Protection measures shall help the regeneration and conserve the species diversity in this Botanical Garden and Eco-park.