Information on the physiological mechanisms of the development organs, such as leaf, of fruit tree crops is still limited, especially in tropical mangoes. Therefore, the leaf morphological characteristics of the mango cultivar named ‘Harumanis’ that have been planted under different conditions (i.e. open-area and greenhouse) were evaluated. Various sizes of leaves from selected Harumanis mango trees were randomly collected and analysed. Data on the leaf area (LA) (cm²), leaf width (LW) (cm), leaf length (LL) (cm), as well as fresh (FW) (g) and dry weight (DW) (g) including leaf moisture content (LMC), were measured and compared between these two growing conditions. Results indicate that the LA, LL and LMC were significantly different (P<0.05) between both growing conditions. The LA of Harumanis mango trees planted in the greenhouse was approximately 25% larger compared with the trees planted in the open area. Similarly, Harumanis trees planted in a greenhouse had 11% longer LL and contained higher LMC than the trees in open areas. However, no significant differences were recorded on LW, FW, and DW between both growing conditions. Our results, therefore, suggest that different growing conditions may have affected the characteristics of tree organs, such as leaves, that may contribute to the environmental adaptation and tree productivity of this high-value mango crop.