<p>Epidermal micromorphology of leaf offers a consistent and taxonomically informative combination of traits to separate closely related plant species. Although <i>Thunbergia</i> has ecological and medicinal implications, there is a lack of systematic comparative epidermal research of <i>Thunbergia</i>. This study examines the epidermal structure of the leaf of six species of <i>Thunbergia</i> that are found in Assam, India, through Light Microscopy (LM) and Scanning Electron Microscopy (SEM). Close examination of epidermal cell patterns, stomatal structure, trichome richness and cuticular ornamentation showed a great deal of interspecific variation with high diagnostic power. <i>Thunbergia coccinea</i> had significantly sinuous anticlinal walls and <i>Thunbergia grandiflora</i> and <i>Thunbergia laurifolia</i> had more or less straight epidermal boundaries with similar stomatal organization, suggesting that they could be closely related. <i>Thunbergia coccinea</i> had the greatest stomatal index and had the most structurally complex trichome assemblage, with papillate glandular trichomes that are similar to specialized secretory structures found in model taxa. The echinate trichomes were abundant in <i>Thunbergia alata</i>, which is a unique diagnostic characteristic. The papillae on trichome surface in <i>T. grandiflora</i>,<i> T. laurifolia</i>,<i> T. fargrans</i> and <i>T. alata</i> show a promising character to this genus. The micromorphology of the cuticle, between rugose and folded structures and finely striated textures, also enhanced the differentiation of species. These characters can be used in combination to create a coherent set of micromorphological markers that can be of great use in delimiting species within the genus. It is also found that the specialized trichome structures have potential ecological and pharmacological implications, which should be investigated further in terms of biochemistry.</p>