Eurycoma longifolia Jack is one of the important medicinal plants in Indonesia and is used in many traditional as well as modern medicine. Until now, there is no information regarding the trichome characteristics of E. longifolia and its relationship with environmental factors is unknown. The purpose of this study was to investigate the morphology and density of the leaf trichomes of E. longifolia, and observed its correlation with geographic and climate factors of population. The morphology and density of the leaf trichome of six populations of E. longifolia were investigated using a light microscope. Analysis of variance, correlation analysis, principal component analysis (PCA), and clustering of the population were performed. The results of this study detected two types of glandular trichome in the leaf of E. longifolia, namely peltate and capitate. Analysis of variance showed a significantly different density of trichome among populations. Inter-population variation in trichome density may be caused by different micro-environmental of each population and genetic factors of plant individuals within population. We confirmed that geographic and climate factors of the population have significant positive/negative correlations with types and density of trichomes. The PCA analysis exhibited that trichomes density could be used as a distinguishing characteristic among populations. Analysis of PCA and UPGMA divided population studies into two groupings.