Trichomes are specialised structures that originate from the aerial epidermis of plants, and play key roles in the interaction between the plant and the environment. In this study, we investigated differences in trichome phenotypes in four lines selected from the S. lycopersicum x S. pennellii introgression line (IL) population for their differences in trichome density, and their impact on plant performance under water deficit conditions. We performed comparative analyses at morphological and photosynthetic levels of plants grown under well-watered (WW) and also under water-deficit (WD) conditions in the field. Under WD conditions, we observed higher trichome density in ILs 11-3 and 4-1 and lower stomatal size in IL 4-1 compared to plants grown under WW conditions. Intrinsic water use efficiency (WUEi ) was higher under WD conditions in IL 11-3, and plant-level water use efficiency (WUEb ) was also higher in IL 11-3 and M82 in WD plants. The ratio of trichomes-to-stomata (T/S) was positively correlated with WUEi and WUEb , indicating an important role for both trichomes and stomata in drought tolerance in tomato and offering a promising way to select for improved water use efficiency of major crops. This article is protected by copyright. All rights reserved.