Although Karachi city is one of the world’s fastest growing cities and considered one of the largest cities of the world, not much is known about its roadside trees. The roadside trees of different types of roads (e.g. Wide roads, Medium roads) in Karachi city of Sindhi, Pakistan were studied. Based on the field sample survey, tree species diversity of different types of roads were examined through different diversity indexes. Furthermore, the relationship between above ground biomass and biodiversity was studied by linear regression model. A total of 180 plots were surveyed, which were divided into three main types of roads. The most significant amount of tree biomass per unit area was found in Wide roads 4.27 kg/m², followed by medium roads. The least biomass per unit area was found in the narrow roads, where trees biomass per unit area was 2.44 kg/m². A single or a small number of species dominate in the observed area that decline the species diversity. A nonnative species Conocarpus erectus revealed dominance which was followed by Guaiacum officinale on all types of roads. Overall, 76 species (32 nonnatives and 44 natives) were noted, which were very disproportionately distributed in the roadside of the city.